If the phone is not working, I suspect that your phone line has become disconnected on one line. That would cause lots of disconnections and poor speed.
If there is no dial tone then you need to report it as "No Dial Tone" . Do not mention the broadband problem, otherwise it will end up in the wrong fault queue, and take much longer to be fixed. There are plenty of people who can fix phone faults, but not as many broadband people.
Once the phone line is fixed, then the broadband will get better.
If your phone is not working when you connect it to the test socket in the master socket you need to do as was advised by Keith in message 6, contact BT and report a telephone fault.
Your broadband will not work correctly if your phone line is not working correctly.
EDIT: Post crossed with Keith's.
No it was something to with the phone, it wouldn't work in the test socket or the socket on the face plate but the wireless phones still work when plugged in to either socket
Is there still a buzzing noise on quiet line test like you reported earlier. If so report phone fault to 151
Yeah but I don't know if it's because of the wireless phone because I know they can be noisy and it doesn't sound like the line noise I've heard in youtube videos