MTM keeps on suspending my contract line

My name Celani Ralph Ngwabe I'd no *** , I have been using MTN contract for last past ten years and last year mtn has been given me problems, my line is is being suspended now again and when I phone them they told me that had a problem where by they did not allocate my March 2020 payment. They said they will resolve the problem and the line will never be suspended ref. No *** The line was suspended again and I ask them to open the line again ref. No. ***. My contract cell number in question is ***. My contact number is *** since the the other number is been frequently suspended. I wish to know which legal action I can take against MTN cause I feel I'm paying for nothing. My email address is ***