Hi Angela and welcome.
I think that the confusion is regarding what is called LLU (Local Loop Unbundling). A number of telecom companies have paid to install their own equipment in BT exchanges, and where these are available they can offer generally lower price deals. If you go to
this page and enter your phone number and postcode you will see which if any are available to you.
If, as seems to be the case, none of them are, then your options are limited to an ISP which delivers its service over the regular BT equipment. This won't change your speed, but you might get a lower price. There are lots of these, and
these pages may help you decide, but if you want more explanation please feel free to ask.
As UncleUB said, a better option might be to see what can be done to improve your connection, and your line stats would be a good start.