Poor customer service and HUGE bills

I took out a contract with MTN for an iPad and 1GB top up at a cost of R329/ month. Every month I receive a bill higher than the last. How is this possible if it is a top up contract? I asked for it to be capped after the 1GB given through the contract every month and was told that as it is a top up contract, that is what would automatically happen. For the month of March, my iPad bill was R689.78. For the month of April, my bill was R1067,14. For the month of May, my bill was R1849,62 and who know what outrageous amount it will be this month? <br> <br> I have been into MTN stores numerous times and even contacted customer care via email and all that I have received from MTN are two reference numbers (#***5 and #***7) and a promise to respond to my email.<br> <br> I am very unhappy with the service and would like my data to be capped as it seems this is not the case and for MTN to look into these outrageous monthly bills.