MTN CONTRACT PAYMENT DISPUTE AND BAD SERVICE

I recently got a contract with MTN and had a dispute regarding a payment i made into acc in February and March , the requested my bank statement as proof if payment with payment ref of which i sent , the outstanding amount still show on my invoice ,after many calls and store visits and talking to many agent , they tell me the matter is in legal and i need to send another proof of payment ,no one contacted me or even updates on the disputes , the service is poor and won't even give me a complaint number . I have the emails as proof even sent a complaints via mtn website and tweeter no response . MTN do not respect me as their client .. need this sorted asap , Thank you.