Data and Voice Billing + Credit Limit Campaign

My Credit limit went from 500 to 3K (apparently to avoid simcard being blocked) and when I queried this no one assistance over two months, and the all of a sudden my bill was 2K+, I asked how this happend, I am told there was a SMS campaign in April and I responded yet, which is totally incorrent. Funny thing is this credit limit changed in the past 2 months from a alleged April campaign. I have been requesting my early termination amount and all i have been getting is the run around and still being charged ridicious amount of money. on the 24th I got an SMS to say that I have reached my limit of 650 and my line is suspended. What Happened to the 3K that I apparently accepted as an increase?? There is a lot of discripancies with these invoicing. ever since I moved from Nashua to MTN its been downhill from there. My handset is insured yet I still paid cash to get it fixed. I have 2 months left on my contract, to someone