2002 Volkswagen Passat My A/C wont work

Hi I have a problem with my air conditioning, the compressor turns on it was recently recharged last year and is still reading full but all I get is hot air coming out of the vents. This first started that I would be driving and the a/c would get hold I would have to turn it off and back on and it would be cold again but then again it goes hot. That happened for a while then all of a sudden it just stopped blowing out the cold air I dont know whats going on can you help me.