MTN overcharging and blocking my account

It has been a month since I've been contacting MTN to correct my account being overcharged... which in turn, they have blocked my data usage. Data which I have paid for.

I have been back and forth with the call centre, Facebook staff and their head office but I keep getting told that it's been escalated to the billing department and then receive a reference number.

Does anyone know of someone who can help?