Please reinstate debit order mandate.

I had a phone contract with Vodacom and they wanted to debit my account last year in December and they found no money because that time my salary was not in yet and they have terminated the Debit order mandate. Please advise why are you not calling to reinstate it so I can continue paying again. I have been calling and sending emails but no one is coming back to me. I can't go to the store because I'm busy.