email changing
 

is there a way to block users \ user groups from changing their own emails
in the user control panel ???

thanks in advance

Not with default vBulletin.

Why would you want your users not to change their email?

i want to restrict users to their ISP emails

to prevent banned members from getting into the forum again

So what you actually want is to disallow the use of free email services?

yes pretty much

You can list the email domains that you do not allow in the vBulletin Options. This would be a better solution then to not allow email changes for your members.

would it apply to members trying to change their mail
or just at signup ?

It would apply to a new email set by an existing member or new registrations. If it will also block existing users that already use such an email address depends on the options you set.