While most phone numbers that use the prefix 555 are ficticious and typically used in movies to prevent people from prank calling someone (similar to the issues caused by the song 867-5309/Jenny), there is an actual phone number that is functional in that range.
If you need to find someone in a particular area code, all you need to do in the United States is to dial the area code and the number 555-1212. This will connect you to directory assistance for that specific area and allow you to find the information you need.
In Australia, 555 was a standard exchange number for a while and was in use. Gary Larson, who drew The Far Side cartoons, once had a published piece that showed a 555 phone number that allowed people to talk to Satan. Since the cartoon was published internationally, the poor Australian bloke with that number got plenty of harrassing phone calls. He tried to sue and lost, but I'm sure he went through hell for a while.
Iron Noder 2017