If you want to remove your BBM (BlackBerry Messenger) ID, you’ll notice it’s not that easy. But I can tell you: It’s possible. All you need to do is follow these 4 steps and pictures below and in 4 clicks, your account will be gone.
This is how I closed my BBM account using an iPhone (but steps remain the same for a Blackerry or Android device):
1 Go to the inbox of your email
by that, we mean of course the inbox of the email address that’s linked to your BBM account.
2 Search for the Blackberry ID account activation e-mail
You received it upon creation of your Blackberry messenger account. The subject was: Your Blackberry ID has been created.
3 Delete this Blackberry ID
is a link you’ll notice when you scroll down to the bottom of the activation e-mail.
4 Continue the removal procedure
to delete your BlackBerry ID by clicking the button on the bottom of the landing page.
Your BlackBerry ID removal request has been completed. The profile has been deleted.
Source (& thanks to): BBM app for iOs devices