Activating an iPhone 5C to use prepaid cards
I want to take my old iPhone 5C and set it up for my 12 y.o. son, primarily to use for "emergencies" on the 2-3 days a week he's in school, which will give my wife and me some peace of mind.
Instead of adding this phone to our wireless plan and having him tap into the unlimited data, we want to go the prepaid route and use the AT&T prepaid cards (available at Target, Best Buy, the grocery store, etc) to add minutes on a monthly basis. I have a new sim card in the phone which will allow it to do the prepaid thing. I can start the BYOD (bring your own device) activation process online ... the website accepts both the IMEI and ICCID numbers. The activation fee ($30) is waived, but there's a $40/mo charge to add it to our plan, which is -NOT- what I want to do, nor is there a way to change it.
So I contacted support twice. The first time I was told the monthly fee would be half that amount, and it would appear as such on our bill. The original sim card ICCID wasn't accepted on the website, hence getting a new one. That conversation ended with no successful resolution. Second time I chatted with someone, I was told that the prepaid cards work in addition to the monthly fee, so I would be paying $40/mo -PLUS- however much I add via prepaid card. This doesn't seem to make much sense to me, and that chat finished unsuccessfully, too.
Maybe I'm misunderstanding what I can/cannot do with this old phone and any prepaid options, or maybe the agent I most recently chatted with misunderstood.
Am I doing something wrong here, is there a step I'm missing?