Bad customer service and breaching of contract

2 months ago I received an SMS stating that I will receive my monthly data the 17th of every month instead of the normal 21st. My debit/payment date has always been the 2nd of each month and now after the change has been done (WITHOUT MY CONSENT) I receive SMS's to say that MTN has suspended my ability to make calls or anything due to non payment. Every single time I have to go to a MTN shop and still it has not been rectified. This is unacceptable as this is breaching of contract. Will definitely cancel my contract next year. This is ridiculous as 2 months in a row this has happended and still it has not been rectified. Worst of all I have to take time out of my holiday as I had to go to a shop on the 24th of December!!!!!