Generally most old information is not deleted, but marked as "depreciated", meaning it is old and not currently in use. If you have confirmed information that their old frequencies are no longer in use, submit this information so they can flag the frequencies as appropriate. Be aware that often an agency will keep their old frequencies around as a backup so even if they are no longer in active use, they may still be available and useable in their backup role and as such are still actually should be kept around.