New contract overcharges

Been calling mtn retentions for the past month and till today my issue hasn't been resolved. I got overcharged twice and all billing keeps on saying "its prorata amount" how can one pay prorata twice. Today I called again & spoke to a rude Paul from retentions who decided to hangup on me when I told him to copy me on the escalation email he was to send to a Lereko who promised to resolve the matter with a senior feew weeks back. I am so fed up with MTN's useless service I think it will be best just to cancel the stupid contract because their people just don't know how to do their jobs. Everytime you call all the do is "escalate" but nothing gets done