You really need to check your line with a cheap wired phone to see if you have dial-tone at the test socket.
Buy a cheap (less than £10) wired phone to run a check.
Then dial 17070 (free call) and select option 2, quiet line test, and see if there is any noise on the line.
If you do not get dial tone, or there is noise on the line, then you need to report it as either no dial tone, or a noisy line. 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 fault is fixed, then the broadband will get better.
Its also worth checking that the phone number that is announced when you dial 17070, is in fact the same number as on your phone bill, just in case you have a crossed line.
This can happen if there is cable work, and the cable pair records are wrong, and you are now connected to the wrong circuit.
On Tuesday builders cut through a cable disconnecting all my street. Open reached fixed the fault. All my neighbours where reconnect yesterday, but BT can't be bothered to reconnect me. The people from open reach or BT came to my house to check the line and confirmed it was all good. They literally just can't be bothered to reconnect it yet. Costing me data money.
Is your phone line working, and is it the correct phone number?