How can i fix my radio cd player?

When i installed my MP3 radio in my astra 1999 model it worked perfectly, but when i store the radio stations they stay on the presets while the key is in the ignition so when i get back in the car there not stored there all back at 87.5 fm.

also the sockets for the radio normally only take 2 but in my astra there 3 sockets so I'm not sure if that woulds affect the stations.