Individuals identifying themselves as AT&T Service technicians are calling private residences and informing individuals that they are conducting tests on the telephone lines, and that in order to complete these tests, the owner needs to press the following keys: nine (9), zero (0), the pound sign (#), and then hang up.
PLEASE BEWARE! By pressing this sequence of keys and hanging up, you give the requesting individual full access to your telephone line which enables them to place long distance calls that are billed to your home phone number.
Apparently this scam has been originating from many local jails/prisons. This information is from a very reliable source and was verified with UCB Telecom, Pacific Bell, MCI, Bell Atlantic and GTE. Please beware and pass this information on ...
DO NOT Press 90# for ANYONE.
Update: The 90# scam is only is a problem with large, organizational phone systems, and not personal residences. There is more information on this matter at: TruthOrFiction.
However AT&T warns of a similar call-forwarding scam in which automated messages are left on residential phones directing people to dial a 2-digit code preceded or followed by the * or # key in order to claim a prize or money. The AT&T Consumer Tips site has more tips for protecting yourself from scams involving residential and cell phones.
Remember, if it sounds fishy, it probably is. Don't press * or # for anyone. Just hang up.