Dexcom and Wireless Provider

My daughter has been using a Dexcom G5 for a few months and I’ve come to rely on it. It makes me feel better to know that I can track her BG at anytime from my phone, and if I see a low starting I can get a snack to her. We’ve added her school nurse as a “viewer” so she can track her BG from her office…also a wonderful blessing.

I bought her a used Apple Iphone 5 and activated it using Walmart’s straight talk prepaid service. Their “basic” plan is unlimited voice, texts and 5Gig of data for $45/month. I’m willing to pay this for the peace of mind, but realistically…she’s 7. The voice and text capabilities are unnecessary, and she’s using about 500Mb per month.

Does anyone know of a wireless service that provides data only that could provide the basics for less?

I pay $35/mo for Sprint pre-paid, but that was before my son was diagnosed with T1D and now I am searching the same options for his Dexcom.
I found an Iphone for sale on the Apple store to connect to AT&T wireless prepaid, but I too am questioning how well this will work.