Help required

When i moved into my house i moved my Gas from British Gas to SWALEC and i paid by direct debit each month. When recently they came to read my meter they read my Electric but not my gas and i said what about the gas and they replied i haven't got gas with them. I said i had but dont have any bills as i shred them they said they would look into it and leave it with them. But so far i have heard nothing , now i am getting a bit worried as i have no idea how long this has been going on for. Obviously i have been using gas but for how long ? what would i owe and to who. SWALEC has said i am not with them no one has sent me a bill and at the mo have no idea what to do. Any ideas please.

ohh.. that was worst then..

can you still remember the person you talked to when you first change your gas from British to SWALEC??