Cell c blocked my phone even when it’s paid up.

I have a contract with cell c which I have no desire to upgrade. They handed my account over to legal attorneys . 18 March 2020 I paid it off and got a paid up letter from the attorney. I’ve been calling cell c since 18 March to unblock my phone since it was blocked by a serial number . I make a call every three days promising me they will call me back to date I haven’t received any feedback. Apparently they are able to work from home but they can’t resolve my query . I’m sitting with a dead phone but it’s paid up .