MTN ABSOLUTELY DISAPPOINTING

After trying several times requesting assistance from staff at the MTN call centre only to be met with the response with that they cannot assist further or resolve my matter I have no choice but to write this complaint then hopefully I will at the attention of someone who can help me. My MTN data contract of R300 was going to end in January this year so I called MTN to find out the way forward, it was then I was advised by a call centre agent that if I do not want to upgrade my contract the service will continue on a month to month basis at the same amount of R300, seeing that they did not have an offer to my liking I settled for the month to month plan. Come end of February I am debited for a whole R1300 so I call to query this massive debit and this time I'm told I am being billed out of contract and there is nothing they can do about it, this is something I was not advised on neither will I agree to such an amount for data only. I asked the very unhelpful agent to log a dispute for the money that was debit which she agrees to but today I call back and told the exact samething I was told before logging the query, that nothing can be done... I requested to be put through to the billing department or speak to someone In a higher rank and this was also denied. I really need someone to assist me with this as it goes against my consumer rights and I am told this will now affect my credit history. I've been a loyal customer with MTN for many years but have been taken for ride and spoken to like my problem is my own and they can do nothing to help me as I'm not willing to pay so much in these difficult times.