I have a dev org and have been working with omnichannel. After working with omnichannel for awhile(about 2 months) I was no longer able to log into omnichannel. I checked the console and it said  "Login Failed" ...."Data Storage Limits Exceeded". So I went to check my data usage and found out that I was maxed out at 110% of my data usage. Most of it(over 50%) was being used by "User Presences" records(over 1400 records). I have identifiyed these objects as "UserServicePresence" records, which can not be deleted. So now a am maxed out on my data and can not delete what is causing it to be maxed out. If anyone can find a way to delete "UserServicePresence" records, I would really like to know.