Frequently telephone outlets are wired by using a daisy chain system. That means that the main wire goes into room #1's outlet, then a wire runs from room #1 into room #2's outlet, then from #2 into #3's outlet, etc. It is weird that only your one outlet doesn't work, but it could very possibly be at the tail end of that daisy chain. If you are fortunate enough to have access to the wiring pattern (and unfinished basement for example), you may be able to identify where the wiring for this particular outlet orgininates (in other words, what room's outlet was it daisy chained from?). Check THAT outlet and make sure that all of the wires are secure.