Hi,
So, I'm no longer with BT, left months ago and BT cancelled gamepass at that time. However it's still showing as purchased from BT on the Xbox Account.
I do still have access to gamepass as I did have 5 months remaining on my own subscription BEFORE I took the BT one which I'm assuming is actually what is being used up.
I phoned Microsoft and they told me it's happening a lot they get lots of contacts about this and there is literally NOTHING they can do on their end and to contact BT about it.