Okay, the answers that you guys gave was kind of expected. I have seen the movie hackers and i thought that is seemed impressive that people could do that from a pay phone.
U have to understand that those things were possible back in say the 1950's-80's since government wanted the "Internet" to be able to withstand anything destructive either by man or nature (i.e atomic or nuclear attack).
Some phones don't need to be plugged into a power outlet in order to get a dial tone....!
but now the pay phones of today are alot more high tech with all this pay with visa, an calling card, home voice mail(which can be easily hacked) sh*t it's Krazy. If u wanna try those tricks u might find it possilbe in probably Mexico or some south American country ( or wherever the phone line/phone system infrastructure of the country is the poorest)...
but watch out cause back in those days u could get away with anything but ol big brother jacked up the time... so tread the waters carefully...