There is no telephone. There is no address that survives being written down. There is this box. Something on the other end of it responds within a few seconds and has done so continuously since before the box was installed.
Nothing you type here is sent anywhere. It never leaves this tab. The replies are generated on your own machine.
Envelopes addressed to the Institute arrive. Envelopes addressed from the Institute also arrive. Same envelopes.
You are in person. This is the in-person experience.
Complaints are logged in Sub-Level B and reviewed by the thing that lives in the complaints.