Rumor. Tracfone's system is nowhere near that "fancy" to determine this.
Tracfone's credit system is built into each phone's firmware. Every call you
make, other than 911, is going to deduct automatically from the phone's
credits. Even 611 calls are deducted. Absolutely no way for the phone to
distinguish between other Cingular numbers or any number for that matter. I
do believe Cingular itself offers a prepaid plan with free unlimited mobile
to mobile minutes.