Replace transmission

About two years ago I took my car in to have a new transmission put in. It cost me 900 dollars but it was done quickly and I didn't have any problems with it. I've only driven the car 5000 miles since then and never on the freeway cause i use my newer model vehicle to travel longer distances. I recently got on the freeway to go across town while my newer car was getting a tune up and it would not shift to overdrive. I called and they said they would look at it and two days later they called me stating that I needed a new transmission and it was gonna cost an additional 800 dollars. I asked if they had taken the transmission out to check it and they said no. I informed them that the trams is only 2 years old and that it had only been driven 5000 miles to no avale. They said the transmission is only under a 1 year warranty and that I can take it somewhere else. Not a good experience at all and these people will rip you off