Can't cancell contract

I have been trying to cancel a contract for 2 months, calling there customer service 082111 every time holding on for 38 min to 60 min just for the call to drop. at the stores they say I have to phone to cancel. How do you cancel if they don't answer their phones. they do phone to upgrade your account, but when you ask them to cancel they refer you back to retentions and start all over again. I just want a contract cancelled????