The other answer is incorrect.
In Gen 4 (which includes Pearl), you need six badges for that Poliwrath to listen to you. If you have 4 or 5 badges, Pokemon up to level 50 will obey you, which means your Poliwrath is over the limit for a Trainer with 5 Badges by 4 levels.
Beat Byron and Pokemon up to level 70 will listen to you, which means your Poliwrath will begin to listen to you.
http://bulbapedia.bulbagarden.net/wiki/Obedience#Badges
In the Gen 5 games, 5 Badges would mean your Poliwrath you listen to you, so you mast have gotten mixed up.
