Same problem AGAIN!!! COME on MTN

After a loooooong struggle to sort out the below, Mtn corrected the mistake only for one month and gave me only 5 gig instead of the 20 gig day and 20 night that I pay for every month. I actually thunk it's time for me to cancel this contract, but then I will probably have to pay a cancellation fee even though they are in the wrong. I will never never never go with mtn again, NEVER!!! This was my previous complain recently.... We took out a data sim contract in january 2020, we took a 20g night and 20g day 24mnth contact, the first month it was finefrom there it was downhill all the way...the second month and every month until now we have only received a third of the data. We have called mtn twice sometimes 3 times per week. The only thing they do is log a call the whole time. No one ever gets back to us. We have emailed the agreement to 4 different agents and not one has come back to us. We get emails saying that the ticket have been closed but the problem still exists. What does one do from here...? If you wanna CANCEL the contract they will ask u a cancellation fee even though they did not hold up their part of the deal. It has now been almost 5 months that we are paying the full installment for a service we are not getting. TERRIBLE TERRIBLE SERVICE I would surely not recommend mtn to anyone.