leaving BT price increase, disincentives/penalties OFCOM

OFCOM say Line Rental Saver should be proportionally refunded when leaving within 30 days of the notification of a price increase. The Guardian newspaper has written about this 26Nov2017. Some BT staff still tell people they will lose any line rental saver paid upfront.

One thing not covered in the press and forums regards mobile sims with BT that are "discounted" if a broadband account exists for the property, this includes sims that are paid for and contracted to the broadband account holder AND any other persons at that residence who have their own separate sim contract with BT.

So when you sign with a new provider after notifying BT you want to leave "because of the proposed price increase" You will receive a system generated email that says you will no longer receive the sim discount and the price will increase after 31 days. Surely this is a penalty or disincentive to leaving BT and in this case is contrary to OFCOM 9.6(I think that's the ref). Also I suppose anyone who independently has a discounted sim will see a rise in their monthly charge?

I have been told that you cannot terminate the mobile sim contract because it is a separate contract.

My question is How can it be separate if it has linked conditions with the broadband contract?
Should we be allowed to cancel the sim without penalty charges if BT intend to raise prices (calling this a loss of discount) when we leave because of broadband price increase?