I switched from Shell Energy on 15th November 2023 and have only released I am still being charge £29.85 for three months. I was told BT would do all the cancelling!
Welcome to this user forum for BT Retail phone and broadband customers.
If you were on an FTTC (copper) connection with Shell, and moved to a full fibre connection with BT, then Shell may not have been told, as it would not have affected the copper connection as BT were not taking over it.
Did you move to full fibre (FTTP) with BT Retail?
Yes I was on copper then swapped to full fibre
Then BT would have treated it as a new order, as they would not be taking over an existing connection, so they would not have informed Shell. The same would have applied if you had moved to BT from Virgin Media, who have their own network.
People could have full fibre and still retain a copper connection with another provider.
Assuming your BT Full Fibre connection is now working, you need to contact Shell and cancel your copper connection.