Mweb Mess Up

I have been using Mweb fiber for a couple of years then I had to move. At the place I was moving to does not have Fiber so i had to change from fiber to LTE. So I switched from Fiber to LTE and I cancelled my fiber, but the the person I was talking to did not cancel it. and I only noted at the end of the month when I was billed twice. I tried sorting this out with them but they have been redirecting me from one department to another. Now I have been struggling to get a new service provider and this has affected my work. WHY DOES MWEB NOT TAKE LIABILITY FOR THIER ERROR AND APOLOGISE.