Can all UK telecom providers forward your calls on request?

[Sebastian Strong]

I'm being told I can contact my provider (BT) if I want to forward my calls, but can all providers do this? And would I have to pay for such a service?

 

[Desert Dust]

I forwarded calls for customers when it was an emergency situation like a house that had burned or something along those lines, but not just because the customer was too cheap to buy the service.