De*****ed by MTN

Hi, i have been loading airtime on my phone a number of times and it disappears before i could even make a call, i have called MTN for them to sort this out but nothing has been done they tell me the same thing every time that they will get back to me which they have not. I am very unhappy with your service MTN i wish i could cancel my contract with you guys right now, you have become the biggest ********