Hi,
I can see you have been given some good advice here, but just getting any banding removed without first fixing the issues is not really going to help you all that will happen is the banding will get re-applied.
Also there are some that don't like smaller companies and try to imply that the ISP has placed a banding on the line this is completely wrong, the process is all automated not someone sitting there trying to upset customers by slowing your speed down for no good reason.
Once you are out of office hours, then try what has been suggested with the test socket and router only with no phones or anything else, and it will need to be the test socket not just the master socket.