Been with them for around 3 years. Never had a problem.
Most likely just either a fault or your specific location, I'm getting 73 down and 20 up.
Check what your line supports on OpenReach webpage. Might find that's all your line is capable of and there's nothing anyone or any supplier can do....
Erm, you meant to say 'Up to 55mb' ... You should have also ran the check up yourself.
As far as I know they are not allowed to charge extra for landline if mandatory. That said there may not be one.