Over charging for last month of MTN Lte contract.

Please stay away from MTN, they rob people of they hard earn money.My wife had taken up an Lte contract in August 2020 with MTN. It's a 24 month contract, which she agreed on R299x 24 months,now we got an sms stating to pay R1124.84 which is payable by 31July 2022,How is this possible MTN?We don't want to pre mature cancel our contract.The number in question is ***.If this matter is not resolved we will go to icasa.