Rian deducting unauthorised money

I have canceled my rain and was advised that the last payment wil go off end of September. Now since 25 October they keep trying to debit my account. I laid a complaint and was told that they did not receive my router back but will investigate as i said they collected. The lady confirmed they will not debit my account because of the investigation.I have send proof that the router was collected by their couriers and also confirmed with the couriers that is was collected and delivered to rain. Today the moment i got money in my account they debited my account. When i call customer service they just dont answer the phone