I'd sure hate to be in this situation. I'd sure be mad if I spent money to have someone look at/repair my inside telephone wiring only to find out later that the problem was with the TWC provided telephopne service!
Did you ever have this problem BEFORE you got TWC telephone service? If no, I'd keep after TWC to fix the problem.
If you absolutely have to get help for your inside telephone wiring, an electrician should be able to do the work, but I'd personally look for a handyman type that has telephone wiring experience to hopefully save some money.
You need to verify that the jumper is unplugged in the network interface box outside first.
Maybe geek squad works on inhouse telco wiring or find an electrician with actual AV experience which many do not have.