Persistent Harassment of an Innocent Old Lady by Cell C Fibre to the Home

We have diligently paid our Cell C Fibre account, yet for the last 3 months we are constantly harassed, especially my elderly mom because the account is in her name because she owns our home. We keep getting messages to say we are in arrears, that our account will be suspended, and even our service has been suspended. Then we call in, we are asked to send proof of payment, the service is reactivated, and we are promised that the problem will be fixed, but it persists. I would also appreciate some advise on how to lay a complaint of harassment with law enforcement against Cell C Fibre, as we are feeling thoroughly harassed at this stage. My payment reference is GN0324-H372