MTN cancelled my contract without my authorisation

MTN has debited R30 000 from my account for 2 consecutive months, apparently for an early cancellation of my contract. My number was ported from MTN to another cellphone network without my permission or a notification from MTN. I entered into a contract with MTN, and I don't understand how they can just allow my number to be ported and then cancel my contract without my permission, whether verbal or in writing. The porting of numbers has made the news recently, due to there being ********** activities linked to this so its very disappointing that MTN does not first find out from their customer if the port is valid and instead just cancels the contract. I have spoken to MTN about this issue for 2 months now and I haven't received any assistance. Instead I have had to block their debit orders which has resulted in them charging me additional fees. MTN fix this problem!!!!!