My data has not been billed correctly

I have a contract with MTN and i recieve data on the 15th of every month.<br> <br> Am not happy with their service at all. My data has been disappearing from my phone like not noboby business. Its two months now this this is happening. <br> <br> I won't renew my contract with MTN if this is what they are doing with customers.<br> <br> Am not happy with the billing system ever since this strike has started.<br> <br> I want my Data back.