REFUSAL TO CANCEL CONTRACT

My first time with MTN was a disaster as i took 2 Data Sim Cards contract with them for 20gb Daytime and 20GB Nighttime. Upon receiving this Sim Cards i called their call centre for activation and during our discussion i also inquired as to how much data i would be receiving and they told me my contract was for 5gb Daytime and 5GB Nighttime and i was surprised by this and requested that they cancel this contract with an immediate effect. They never cancelled the contract and continued to debit my account and i haven't even received the 5gb they claimed the contract was for.

Now they are saying i need to pay them early termination fee which i don't understand what it is for as they are the ones who prevaricated before terminating this contract.

I have never been so disappointed in my life, the service of this institution is so appalling to say the least.