After doing a search I found this thread and I thought I'd thow in a little personal experience. I did not know my account number, but wanted to close my account. I called the following number.
1-866-893-7864
And, pressed (1) for account holders. When the machine asked for my account number I just waited, and eventually I was transfered to a live person. After giving my ss# to a representative. They found and closed my account.
Just a note, I knew I had an account here. And, I also knew they already had my ss#, so I didn't see giving it as a danger. I opened it a few years ago for a specific purpose. I just didn't have any paperwork with my account number on it.