Horrible service

I called fonechoice in June regarding a delivery and followed up on my account and contract end date. I was notified that my contract ends at the end of July and that would be my last debit order. However come end of August I was debited again and now I am being harassed by their debt collection team with up to 10 calls a day. I queried this and was promised that the matter will be referred to their Back office for assistance but they won't stop harassing me with the calls because they can't control the calls. If this is the case then what purpose does it serve for them to call consumers cause answering their calls does not help at all? I am still waiting for feedback from their back office and am infuriated by the lack of respect displayed.