strange telephone happenings

A while ago, I was trying to use the phone and then noticed that it said that the line was in use. I checked all the receivers around the house to check if one might be on, but none of them were. Then I decided to unplug each one and plug it back in. I checked again and it still said line in use. The next morning, someone came by to fix it, but by then, the phone was working again :)