G-28 Mailing address: NBC or Local CIS office when the case is w

Teacher Pjiang indicated that Form G-28 (to terminate attorney) should be mailed to where the case was pending. Our I-485 was transferred to NBC several months ago. And the case was further transfered to local CIS for the interview. We have completed the interview, but PD is not current yet.

Now I wanted to terminate the attorney. Where should we mail the Form G-28? NBC or Local CIS office? I am not sure how long the IO would keep our case with her if it takes too long for our PD become current.

In addition, do we need to send another G-28 for all the previous AP/EAD that had been approved?

Thanks in advice for the help.