change in contract limits with no notification

I recently upgraded my contract, beginning June. At the end of the month i received an SMS saying I have reached my limit of R2500. This limit was never discussed with me - it has been at about R10,000 for the last 2 years as I regularly travel overseas. I called in to query & was told they will request the increase. A month later I get the same SMS, call again to query & get told it will get fixed. This month, 3rd time, I get another SMS - reached my limit of R2500! I went to the store where I upgraded, was told my request was declined! No request for proof of income after being with MTN for +-15 years. I was told to contact the 'contracts' dept. I called on Monday 17th to cancel as I have now had enough