Bad experience

Good morning I have an ugly experience with MTN South Africa I purchased a am MTN home router which they checked my coverage before signing me on but on receiving the router there is no network coverage in my house but I have 7 days window to return it which I did in the 3rd day they received it in the shop gave me a reference number to call the call center to cancel the contact which I did the agent told me it is canceled but yet still debiting my account I keep calling them to stop until I stop the debit order that they can’t debit my account again they took my info to the collection attorney and now my credit record has been seriously affected and they can’t stop calling and sending me payment requests upon all my explanation to the agent. Please can someone help me my name is Victor E Ugochukwu with I’d number ***