BILLING FOR A VODACOM CONTRACT WE DIDNT TAKE OUT - R25 000

R25 000 bill received per email from Vodacom. We last month received a bill from Vodacom for an unusual amount that does not normally go off on a debit order that we have had with them for 4 years. On inquiring at the store we were told that someone has taken out a contract on our name ? Vodacom is not helpful at stopping/ cancelling this contract ,from , after 1 month its R25000 what about next month? Now the bank cant stop the debit order and we have to open a ***** case for a phone that we do not have or signed a contract for. Wh wont Vodacom help and stop this before my salary goes down the drain for something I dont have .