MTN Bad news !!!!!

I have a contract but my my billing is more and more every month I got the app and set it on a certain amount (closed line) but every month my account goes up. It shows on my billing an amount but what they bill is 3 times that amount. Don’t ever take a contract with Mtn. No one can assist you or sort it out. They just don’t care. Terrible service!!!!!!!!!!!!!!!