There are several ways you can get rematches with NPC's. There are four types of NPC's you can battle. You can battle Storymode NPC's like Wilana and Jubilee, Gym and Elite 4 Members with higher (or lower if E4) leveled pokemon, Battle NPC's Random Characters Built into certain Routes to battle and re-battle specifically for experience, and Request NPC's characers from Requests who you can go back and battle. To get a rematch, PM me who you'd like to battle and what rules you'll play under. You can only battle trainers on your current route while in storymode. However, if there is a Story Event in action, you can still battle. Simply Request the Battle and I'll place it in the PvP section. Battles in the PvP section, however, don't reward Exp. Sorry.