MTN overcharging me on purpose (for sure)

Entered into a contract with MTN for 40G anytime and 40GB night time. I am only getting 10GB/10GB … I have made sooooooo many calls but they do not want to fix my contract. And i cant cancel cos i will be penalized. What is so difficult to correct the system to reflect the contract that i signed? It has been 5 months now and STILL NOT RESOLVED!!!