Cant forget a wireless network password.

Hi I live in shared accommodation which has wifi provided by BT open zone. I receive 3GB free usage with my iPhone contract. But now want to buy the actual package so i get unlimited. The only problem is I cant get my Macbook to forget the password, so I can enter my new password for the network. Its really annoying looked at loads of tutorials online and nothing is helping deleted everything to any network i can find and still it logs in fine. Even changed my BT openzone password thats linked to my phone and its still connecting.
Very puzzled and starting to get annoyed any ideas?

Never mind. As soon as i posted this the password changes kicked in (hours after changing them). So its all good now.