Try this:
https://www.att.com/esupport/article...id=jiSs-Xqe7Vv
My iPad is on Verizon's LTE (contract). I wish they did their international roaming different. I don't like having to flip it on and off like a light switch. I would much prefer a small variation in their plan where I could leave roaming on, pay zero dollars a month when there was zero roaming, a step like the first 10 megs were $10, 11 megs to 100 megs were $25 (their current rate), and then follow their plan.
I live close to the Canadian border and I transit through Amsterdam.