Usually the guy I got on the line would give me the phone number for dialing into the switch of his Central Office. But if a tech challenged me, I knew enough about the system to make up a plausible excuse on the fly. It might be something like, "We’re setting up a new dial-out system here and programming all the dial-up numbers into our outgoing dialer software. So if any switch engineers have to dial in, they can just instruct the modem to dial a particular office."