Terrible service from supersonic!

I can't get hold of them on WhatsApp, email and they don't call back should the line drop. You wait for an agent for no less than 25 minutes. The one day I was trying to sort out a problem and was on the phone for 4 hours! I can't cancel their service because I need confirmation from them to release my line.....they never respond. Once that is done only then can I contact a new service provider. Please can someone help me! I'm so so desperate.