Can not upgrade contract expired but just pay for 3 more months

My husband went to MTN yesterday to upgrade his contract that he have had for many years but when het got there they said his contract has expired he can not upgrade and the debit order going off his account is now R135 a month, OKEY so the contract is expired and can NOT upgrade but you pay now R135 to keep the contract open,, hello explain that so then he was told to phone and cancel because what on earth you can not upgrade but just pay some more, phoned to cancel the contract after the phone call he got an sms saying that the contract will be cancelled 10 December and he need to pay until then WHAT according to MTN the contract expired so now they just want more and more money just because really this is so disappointing after so many years this is the service you get