Testing the WAN

My wife is a Telemedicine Coordinator with 25 small rural sites using voice/video to communicate with major Hospitals. They use T-1’s and ISDN over two different Telephone companies who always say the problem is the other guys fault. Is there software out there to test these telephone lines and nail down exactly which line segment is the problem without waiting for the telephone companies to spend 2 weeks before they get around to it?