Go to Shenron after collecting all the Dragon balls. if you don’t get the Shenron you want, exit without saving the game. Instead, head to the options menu and load your data. After loading you should still have your Dragon Balls. Now use them and there should be a different Shenron. Note: Just make sure to save after you get the Dragon Balls but not after you go to Shenron. Remember to choose whichever wish the current Shenron offers you and exit without saving. Now load you data to find a different Shenron.