Mtn is taking my money

I have an MTN phone contract. This year June, I upgraded and keep in mind I had R500 balance. I bought two phones which cost R700, because I had a R500 balance, they were supposed to deduct R950 in July and August because of the R500 balance. From September they were supposed to deduct R700 because I've already paid the outstanding R500, but they still deducted R950. And when I bought one of the phones ( Samsung Galaxy S22) I was also supposed to receive a free adapter. I didn't get the adapter, they don't treat me well. I'm no longer interested in their contract. I'm pleading for your help