Certain services will require certain setup and conditions. Some people cant get Infinity yet and are still on basic DSL. Thats just the way life is.
Excuse me but I have only just been able to get Infinity, it has been some time since I have been able to get the Extra channels available. I was just had to wait until Infinity was available within my area.
Same with any service provider or company not every service will be available for everyone.
Assuming that there's not a fault on your line and it's performing to its full potential with the current FTTC-VDSL2 (profile 17a) technology then you get what you get. Don't hold your breath waiting for any improvement.
Note that some customers on FTTC-VDSL2 fibre broadband can only get 2 - 15 Mbps. In that situation BT call it Faster Broadband rather than Infinity and those customers are even more limited in their BT TV options.