MTN ********* business practice.

I signed a contract with MTN for R 200/month. The contract came to an end and the contract was never renewed. Now they are charged me R 1200/month. I signed a contract for R200/month not R1200/month. The messages sent to me were "You have been successfully authenticated with MTN. If this doesn't sound right, please contact us at 083 135". So I contacted the help desk and the lady at the help desk couldn't help me with what the message was about. I also received a message from MTN "Your authentication has failed. Fror more info or help, please chat to your agent."