Observations of a High School Sub- cell phones & prison

I generally learn more when I sub than I present to the students. I recently learned the following information while subbing:

A young lady was explaining that her sister was mad at her because she missed her phone call from her boyfriend in jail for the week-end. She then went on to explain that cell phones are not able to receive phone calls from jail. Then another girl quickly commented, "No that's not true... My daddy's been in jail for 10 years and he calls my cell phone, You just have to call your provider and get a special code" The first girl responded, "That's good for your dad but it's not worth going through all that for the occasional weekend jail stay"......I hope I never have to use this new knowledge!