Prisoners have been coaxing money from people but cannot be prosecuted because the practice is not illegal.
Pinellas County sheriff's officials issued an alert Tuesday regarding a money-soliciting scam operated by some jail inmates.
According to sheriff's spokesman Cal Dennie, inmates have been calling people, mostly elderly women, by picking old-fashioned names from telephone books such as Esther or Louise.
The inmates call themselves by common men's names, such as Bill or Bob.
If the person has a relative or knows someone by that name, the collect call from an inmate is usually accepted.
Dennie said inmates then solicit money, supposedly for items such as a Bible, toiletries and other things.
"Getting people to accept the (collect) call is called hooking," he said.
"Then they do what's called fishing. They start conversations involving something in common, usually religion. Then they ask for money, going at it from a religious point of view."
In some cases, entire pods of inmates at the jail have been involved in the scam.
An investigation began recently after the son-in-law of an elderly woman complained that she had paid an inmate.
Dennie said detectives were told that at least one inmate had gotten up to $1,000 from people he'd called from the jail.
Inmates have access to telephones and directories at certain times of the day. Any calls inmates make are collect.
No one has been charged, Dennie said, because it is not illegal for inmates to coax money from people.