Battle pets issue

Hello,

Any of you guys collecting or using the battle pets in Azeroth or Pandaria ?

I have a question, regarding how to "dispose" of a battle pet.. How do you get rid of one ??

I click on RELEASE option, and it actually erases it from the list of pets I have, but when later on I come back in the game, all the pets I have erased are back...

Is there a better way to remove a pet from the pet collection ?

Thanks