MTN Claims a contract I never took

MTN has claimed that I am owing them money for the contract that I never took with them. I have asked them to provide me the proof of the contract that they claim I took, which will have the date and time, duration of the contract, the package, my bank account which I should have provided, and the debit order date. They have never provided that. They send different people to call me to remind me about the contract, threatening to blacklist my name. If there was a contract there will be an agreement of the debit order with the bank name, account number, account type, the amount, debit order date, and the duration of the contract, and I will also have a copy of the contract. If there was a contract, why did they not debit my bank account? My ID number is ***. Can MTN please come clean and provide the copy of the contract you claim I took, which will have my signature and the date. I am tired of your agents calling me.