Cellphone Contract

I have just recently found out that there's a cellphone contract on my name which I did not take.. Mtn is now calling me to advise that I owe them as there's missed payments .. The contract not being paid is affecting my credit score as I am not the one who opened the contract ... There's no debit order in any of my banks for this contract so now how did they verify my details and approved the contract ? I am now being told to pay for something that was not done by me... How do they verify documents if it can be easy for people to do this ... They need to get to the bottom of this and investigate the matter because even worse I have never had a contract with Mtn