Data usage on mobile hotspot

I’m a henna artist with a booth at Ocean Beach Park in New London, CT, a location with no internet or cell reception. I need to take credit cards, so I bought a mobile hot spot. I didn’t know how much data I’d need, so I checked my phone usage from last year. I use my phone for everything- navigation to gigs, looking up event info, Facebook always on for both business and personal, playing games, taking credit cards, emergency finding out who was that guy in that movie where he did the thing, and the like. Last year, I used less than 600 MB a month, so I bought the cheapest plan at 1GB per month. Since ALL that it would be used for is taking cards, I figure it ought to be plenty.
I set the hot spot up Friday. I spent an hour or so on my laptop entering information into my cash register app, and since then, the only use has been to take a few credit cards on the app on a tablet. I had some trouble getting the password in, but it should lock everyone else out. Nonetheless, today I got a message saying that my data was all used up. 1GB in 3 days, taking maybe ten credit cards and an hour of data entry on one simple website sounds like nothing near what I would expect. So I called the service provider.
The website for my phone gives me a list of who I called, or called me, and their number, and how long I was on with them. Apparently there is nothing similar for the hotspot. This makes no sense. If they know how much I used, they must have tracked it, no? I am feeling a strong sense of scam here. Is that reasonable? How much data would you expect to have been used? How can I track if my employees are using data without permission?

Auto-downloading system updates? I’m curious how your hotspot works at all if there’s no cell reception.

There are occasional wisps of cell reception. It depends on the carrier. The hotspot gets pretty good service, while my phone gets almost nothing.

Probably an iTunes update.

But, like yoyodyne, I too wonder how you get the hotspot to work where there is “no internet or cell reception”?

I don’t think there’s iTunes on the tablet- it’s Android.

It does sound like the time your laptop was connected for a hour it did things you were not aware of, perhaps spyware, perhaps a update. I would suggest excluding your laptop on this device and jsut using the smartphone with something like the Paypal or Square CC reader. That should solve you woes.
-but-
Have you considered switching carriers as New London CT is not some location in the stix but part of the Bos-Wash megalopolis - it is also flat lands so any major carrier should have great smartphone service. Your mobile hot spot working proves that it does as it works on cellular service.