Customer care not responding to email/ calls

I would like to change my contract to prepaid, but i cannot get hold of MTN<br> <br> I have mailed on the 23rd of May as well as trying to call today 3 times. Holding for 20min at a time.<br> I am currently out of the country and unable to go to a store, calling is very costly.<br> <br> This delay is causing debits from my account that I would like to cancel.