I received a telephone call last evening from an individual identifying himself as an AT&T Service Technician (could also be Telus) who was conducting a test on the telephone lines. He stated that to complete the test I should touch nine (9), zero (0), the pound sign (#), and then hang up. Luckily, I was suspicious and refused.
Upon contacting the telephone company, I was informed that by pushing 90#, 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. I was further informed that this scam has been originating from many local jails/prisons.
Snopes.com: This item is another example of a scam warning that has been continuously circulating via the Internet for the better part of a decade, thereby receiving vastly more publicity than it warrants. Although the warning has some kernel of truth to it, only a very small, specialized portion of the phone-using public is vulnerable to the scam described therein.
This scam does not affect residential or cell phone customers — it only applies to businesses, hospitals, government agencies, and other organizations that still use telephone private branch exchanges (PBXs) rather than Centrex lines to handle their calls. On certain PBX systems (i.e., ones for which pressing '9' is the signal to obtain an outside line, and there are no restrictions placed on outgoing calls), a scammer could gain access to place expensive, long-distance phone calls by tricking an employee into initiating the #-9-0 sequence. Outside of a few other settings where one might have to press '9' to obtain an outside line (such as hotels), the likely result of pressing #-9-0 will simply be a fast busy signal.