Line barred because I want to cancel my contract with MTN

Contract Cancellation, MTN retention have barred my number I can not make or receive calls, after I had asked for my contract to be cancelled. I have been calling the call center and the retention department either put me on hold or just cut off the call. Can mtn attend to me urgently this is my personal and business number I can't afford to have my number barred for no reason just because I want to cancel the contract that already expired in November 22 and now want to be pre-paid