I am having an error in 7 challenge.

My Trigger code is:

trigger ProjectTrigger on Project__c (after update) {
    //after trigger to fire if the Status is set to Billable.
    If (Trigger.isAfter && Trigger.isUpdate){
        for(Project__c proj : Trigger.new){
            if(proj.Status__c.equals('Billable')){
                BillingCalloutService.callBillingService(proj.ProjectRef__c, proj.Billable_Amount__c);
            }
        }
    }
}


My BillingCalloutService class is as follows:

public class BillingCalloutService {
               
    //method to run asynchronously or in future, invoked from trigger.
    @future(callout=true)
    public static void callBillingService(String projectRef, Decimal billingAmount){
        //gets the custom settings values.
        ServiceCredentials__c servCred = ServiceCredentials__c.getValues('BillingServiceCredential');
        //creating the project object to be passed in argument below.
        BillingServiceProxy.project project = new BillingServiceProxy.project();
        project.username = servCred.Username__c;
        project.password = servCred.Password__c;
        project.projectid = projectRef;
        project.billAmount = billingAmount;
                                //synchronous call to the Billing Invoice system.
        BillingServiceProxy.InvoicesPortSoap11 invoiceCall = new BillingServiceProxy.InvoicesPortSoap11();
        //getting the response back from billing system.
        String response = invoiceCall.billProject(project);
                                //if the response is ok, need to change the billing status to 'Billed'
        List<Project__c> proj;
        if (response != null && response.equalsIgnoreCase('OK')){
            proj = [SELECT Status__c FROM Project__c WHERE ProjectRef__c =: projectRef];
            if(proj.size() > 0){
                proj[0].Status__c = 'Billed';
            }
            update proj;
        }
    }
}

BillingServiceProxy:

//Generated by wsdl2apex

public class BillingServiceProxy {
    public class billProjectRequest_element {
        public BillingServiceProxy.project project;
        private String[] project_type_info = new String[]{'project','http://salesforce.com/th/invoice-web-service',null,'1','1','false'};
        private String[] apex_schema_type_info = new String[]{'http://salesforce.com/th/invoice-web-service','true','false'};
        private String[] field_order_type_info = new String[]{'project'};
    }
    public class project {
        public String username;
        public String password;
        public String projectid;
        public Double billAmount;
        private String[] username_type_info = new String[]{'username','http://salesforce.com/th/invoice-web-service',null,'1','1','false'};
        private String[] password_type_info = new String[]{'password','http://salesforce.com/th/invoice-web-service',null,'1','1','false'};
        private String[] projectid_type_info = new String[]{'projectid','http://salesforce.com/th/invoice-web-service',null,'1','1','false'};
        private String[] billAmount_type_info = new String[]{'billAmount','http://salesforce.com/th/invoice-web-service',null,'1','1','false'};
        private String[] apex_schema_type_info = new String[]{'http://salesforce.com/th/invoice-web-service','true','false'};
        private String[] field_order_type_info = new String[]{'username','password','projectid','billAmount'};
    }
    public class billProjectResponse_element {
        public String status;
        private String[] status_type_info = new String[]{'status','http://salesforce.com/th/invoice-web-service',null,'1','1','false'};
        private String[] apex_schema_type_info = new String[]{'http://salesforce.com/th/invoice-web-service','true','false'};
        private String[] field_order_type_info = new String[]{'status'};
    }
    public class InvoicesPortSoap11 {
        public String endpoint_x = 'http://sb-integration-bs.herokuapp.com:80/ws';
        public Map<String,String> inputHttpHeaders_x;
        public Map<String,String> outputHttpHeaders_x;
        public String clientCertName_x;
        public String clientCert_x;
        public String clientCertPasswd_x;
        public Integer timeout_x;
        private String[] ns_map_type_info = new String[]{'http://salesforce.com/th/invoice-web-service', 'BillingServiceProxy'};
        public String billProject(BillingServiceProxy.project project) {
            BillingServiceProxy.billProjectRequest_element request_x = new BillingServiceProxy.billProjectRequest_element();
            request_x.project = project;
            BillingServiceProxy.billProjectResponse_element response_x;
            Map<String, BillingServiceProxy.billProjectResponse_element> response_map_x = new Map<String, BillingServiceProxy.billProjectResponse_element>();
            response_map_x.put('response_x', response_x);
            WebServiceCallout.invoke(
              this,
              request_x,
              response_map_x,
              new String[]{endpoint_x,
              '',
              'http://salesforce.com/th/invoice-web-service',
              'billProjectRequest',
              'http://salesforce.com/th/invoice-web-service',
              'billProjectResponse',
              'BillingServiceProxy.billProjectResponse_element'}
            );
            response_x = response_map_x.get('response_x');
            return response_x.status;
        }
    }
}



Please help me to kick off this error.Thanks in advance

I am having an error in 7 challenge.

My Trigger code is:

trigger ProjectTrigger on Project__c (after update) {
    //after trigger to fire if the Status is set to Billable.
    If (Trigger.isAfter && Trigger.isUpdate){
        for(Project__c proj : Trigger.new){
            if(proj.Status__c.equals('Billable')){
                BillingCalloutService.callBillingService(proj.ProjectRef__c, proj.Billable_Amount__c);
            }
        }
    }
}


My BillingCalloutService class is as follows:

public class BillingCalloutService {
               
    //method to run asynchronously or in future, invoked from trigger.
    @future(callout=true)
    public static void callBillingService(String projectRef, Decimal billingAmount){
        //gets the custom settings values.
        ServiceCredentials__c servCred = ServiceCredentials__c.getValues('BillingServiceCredential');
        //creating the project object to be passed in argument below.
        BillingServiceProxy.project project = new BillingServiceProxy.project();
        project.username = servCred.Username__c;
        project.password = servCred.Password__c;
        project.projectid = projectRef;
        project.billAmount = billingAmount;
                                //synchronous call to the Billing Invoice system.
        BillingServiceProxy.InvoicesPortSoap11 invoiceCall = new BillingServiceProxy.InvoicesPortSoap11();
        //getting the response back from billing system.
        String response = invoiceCall.billProject(project);
                                //if the response is ok, need to change the billing status to 'Billed'
        List<Project__c> proj;
        if (response != null && response.equalsIgnoreCase('OK')){
            proj = [SELECT Status__c FROM Project__c WHERE ProjectRef__c =: projectRef];
            if(proj.size() > 0){
                proj[0].Status__c = 'Billed';
            }
            update proj;
        }
    }
}

BillingServiceProxy:

//Generated by wsdl2apex

public class BillingServiceProxy {
    public class billProjectRequest_element {
        public BillingServiceProxy.project project;
        private String[] project_type_info = new String[]{'project','http://salesforce.com/th/invoice-web-service',null,'1','1','false'};
        private String[] apex_schema_type_info = new String[]{'http://salesforce.com/th/invoice-web-service','true','false'};
        private String[] field_order_type_info = new String[]{'project'};
    }
    public class project {
        public String username;
        public String password;
        public String projectid;
        public Double billAmount;
        private String[] username_type_info = new String[]{'username','http://salesforce.com/th/invoice-web-service',null,'1','1','false'};
        private String[] password_type_info = new String[]{'password','http://salesforce.com/th/invoice-web-service',null,'1','1','false'};
        private String[] projectid_type_info = new String[]{'projectid','http://salesforce.com/th/invoice-web-service',null,'1','1','false'};
        private String[] billAmount_type_info = new String[]{'billAmount','http://salesforce.com/th/invoice-web-service',null,'1','1','false'};
        private String[] apex_schema_type_info = new String[]{'http://salesforce.com/th/invoice-web-service','true','false'};
        private String[] field_order_type_info = new String[]{'username','password','projectid','billAmount'};
    }
    public class billProjectResponse_element {
        public String status;
        private String[] status_type_info = new String[]{'status','http://salesforce.com/th/invoice-web-service',null,'1','1','false'};
        private String[] apex_schema_type_info = new String[]{'http://salesforce.com/th/invoice-web-service','true','false'};
        private String[] field_order_type_info = new String[]{'status'};
    }
    public class InvoicesPortSoap11 {
        public String endpoint_x = 'http://sb-integration-bs.herokuapp.com:80/ws';
        public Map<String,String> inputHttpHeaders_x;
        public Map<String,String> outputHttpHeaders_x;
        public String clientCertName_x;
        public String clientCert_x;
        public String clientCertPasswd_x;
        public Integer timeout_x;
        private String[] ns_map_type_info = new String[]{'http://salesforce.com/th/invoice-web-service', 'BillingServiceProxy'};
        public String billProject(BillingServiceProxy.project project) {
            BillingServiceProxy.billProjectRequest_element request_x = new BillingServiceProxy.billProjectRequest_element();
            request_x.project = project;
            BillingServiceProxy.billProjectResponse_element response_x;
            Map<String, BillingServiceProxy.billProjectResponse_element> response_map_x = new Map<String, BillingServiceProxy.billProjectResponse_element>();
            response_map_x.put('response_x', response_x);
            WebServiceCallout.invoke(
              this,
              request_x,
              response_map_x,
              new String[]{endpoint_x,
              '',
              'http://salesforce.com/th/invoice-web-service',
              'billProjectRequest',
              'http://salesforce.com/th/invoice-web-service',
              'billProjectResponse',
              'BillingServiceProxy.billProjectResponse_element'}
            );
            response_x = response_map_x.get('response_x');
            return response_x.status;
        }
    }
}



Please help me to kick off this error.Thanks in advance