Devastated

I am receiving calls from MBD telling me that I have an account with vodacom that I must pay. When I ask what account they don't know. I never had a contract with vodacom in my life. Been using my number for more than 10years now. I started using this number while I was a teenager. I recently started working and I never had contract with vodacom. They're busy requesting for my ID copy but don't want to provide me with the account number or copy of the contract that They're claiming that I have. When I ask on which day and on which account where they debiting money from, they don't even know. They're even threatening me. Yoh I never had contract with vodacom in my life and I will never will