debited large amount

I had a problem with celc 2 months ago when they have me the wrong contract deal which they rectified after i complained. Now they billed me a wrong among which was rejected because of insufficient funds. They now charged me for debit order reversal fees plus amounts that they say is for purchasing data bundles. I had a problem with this before and i called in and put a cap on my account. A cap is supposed to stop at a certain amount so i don't see why that's the reason. My phones were also blocked for half the month which was because of their error. Cel c promised to cal me yesturday morning to rectify the amount but no one called and i am tired of calling in so many times and explaining the problem over n over