Picked this off another forum:
I received a telephone call last evening from an individual identifying himself as an AT&T Service technician who was conducting a test on telephone lines. He stated that to complete the test I should touch nine(9), zero(0), the pound sign (#), and then hang up.
you give the requesting individual full access to your telephone line, which enables them to place long distance calls billed to your home phone number.
jails/prisons. I have also verified this information with UCB Telecom, Pacific Bell, MCI, Bell Atlantic and GTE. Please beware.