Breach of contract

My cellphone contract finished with MTN SA last year December and I call their costumer centre to cancel in as its usually done. I then requested to be changed to month-month prepaid contact. In January 2020 the package was loaded to my account correctly but then from February 2020 and now in March MTN somehow changed the package. They loaded less data and call minutes on my account.

I called in February to inform them that there has been a mistake, the acknowledged that it was a mistake and will correct it but they never did. Then I thought maybe they are waiting for the new month but again this month the same thing happened. I called again their costumer service, I was on the phone for more than 40min and even running late for my meeting. The person who was helping me (Ayanda) said he will call me back once he has listened to my previous call from February (which was also that long), but he never did.

I just got a message today like the same one I got last month saying my query has been resolved but it still isn't.