30 days of use, 4 iPhones, which plan?

Hello,

I have four phones I'd like 4G data and voice plans for 30 days?

I see you have sim only plans now, but it looks like the plan billing is set up for ongoing monthly. We'll only be in the US for a month so don't want an ongoing service.

I called a NYC T-mobile store and they said "for iPhones it would be 3G" and $50 for unlimited 30 days" (plus $10 sim fee).

This doesn't seem to line up with the web store, and I'm confused about the 3G instead of 4G.

Any advice appreciated on what it will cost and what I will get