I'm contemplating giving an old iPhone to my elderly parents who have never had a cell phone before (they do have an iMac and an iPad, so they are in the Apple universe). They would only be in a situation to use the phone for voice a few times a week, but they'd also use iMessage (all of their kids have iPhones) and maybe occasional mapping (but I don't see them using a lot of data otherwise). I realize that the iPhone may be overkill and they might do ok with a cheaper phone, but I also think they would enjoy the iPhone more even if they would have fewer occasions to use it. It's an unlocked GSM iPhone 5s. I understand the budget carriers that support GSM are: Cricket Wireless, MetroPCS and Straight Talk. I think their touted plans are even more than my parents would need. Are there any post-paid, pay as you go plans?