Inappropriate sales

MTN Sales department when signing me up for wifi told me I need to make a prorated amount and my next monthly debit. Great, no issues with that. Then December and January I did not get data because I was overcharged and the wanted to debit me again for December. MTN customer service and the ombudsman have not helped and the matter has been ongoing for 2months they are not able to retrieve a phone call from their own sales department.