There are 2 cables in a phone line. Calls need both but broadband only needs one so you may have a fault on one of the cables.
Do you have a neighbour who could lend you a landline phone to check it's not a fault with your handset?
Or, do you have a neighbour who could lend you a mobile to call the broadband and telephone helpline?
If not you can use a computer to make a landline call. I'm not going to recommend any one particular service but if you Google 'use a computer to make phone calls' there's a wealth of information!
