Worst ISP support ever! And lies!

When I took out my fibre line they told me there would be no cancellation fees if the line is older than six months, it’s a month to month and I only have to give a months notice for cancellation. My lines older than a year and I have a months notice only to receive an invoice more than my monthly payment. I moved to another ISP because they have a faster line for almost R300 less. I worked it out in such a way that I wouldn’t go a day without network as I work from home. Now they will not release my line to the new ISP (which I’ve already paid) I asked to speak to a manager and got put on hold for 20 minutes, not a word from the agent. I did not cancel because of network issues but because the new ISP had a better offer. But supersonic has the worst customer service and support system! I need my line released asap!