MTN debits my account and says I didnt pay!!

A few months ago I started to have problems with MTN, the deducted money from my bank account and ever since that day I am fighting a battle. They have caused me to get a bad credit record and say my account is in arrears. I have been emailing statements as proof that it went of my account but dont hear anything back from them.

Mostlikely the worst service I have ever received.

What am I to do?