MTN CORRECTLY DEBITED MY ACCOUNT

Good day, I received an sms on the 13th of September saying that my installment will change from R299 to over a R1000. I immediately went to MTN to fix this. Vaal Mall MTN phoned head office and it was fixed that same day to change back to R299 with a new data contract. My Ref no was. ***. I received a contract also via my email. Yesterday the 1st of October my account was debited with R1167.55.. I tried phoning MTN to fix this yesterday but couldn't get hold of anyone... I went this morning to MTN at Riverwalk in Three Rivers but the lady there didn't understand the situation and could not help me. Which is sad.. I think they must get training on these kind of situations... I immediately phoned MTN again on 135 today. The lady assisted me very nicely and said she will send a complaint through as this is not correct.. They charged me incorrectly as this was fixed the same day.. Please pay back the difference in the installment back to me as this was not my mistake it was MTN's.. See ref numbers *** / ***. Please assist me with this problem.. It would much appreciated. Thank you.