Suspending my contract for their wrongs

I signed a mobile contract with Telkom last year December. They ignored the date of debit orders we agreed on, so they debited my account whenever it suits them and again not every month. They will skip a month and debit the following on the wrong date still. This month on the 15th they decided to debit me 3 times so it bounced and they suspended my contract with them. I called them multiple of times they accepted they wrong doing but they did not restore my line. I believe they did not honor their contract with me 1. Wrong date of the debit order, 2. Not debiting me monthly 3. Trying to debit me for the coming month which they do not have a bill already.

WHAT STEPS SHOULD I TAKE I CANNOT CONTINUE WITH THEM?