You just need to go through their questions and I find it easier to call people.
A relative has SKY broadband and was getting asked all kinds of strange questions. I popped round called SKY, after 15 minutes they were happy enough and went away to fix the fault. The trick is to work with them , be calm but don't be afraid to help them jump steps in their scripts to hurry them along. There is only so many places the fault can be in standard home internet, your PC, your router and your internal cabling. After that it is down to your provider to sort out.