MTN CONTRACT

I bought MTN SHESHA plan and it was delivered on the 25th of June and it didn't work when I called them they said it won't work since my area is not covered with 5G, so I visited MTN store to return the router and cancel the plan they said I must go back with the router and try it again then I went backagain on the 30th of June after an agent said I should return it so I will get a refund so I returned it and filled a form to cacel the contract, todays date is the 24th of August they are refusing to give me refund and they are still trying to debit funds from my account.