I just returned from 2 weeks in the BVIs and had my Iphone with me.
I could get a At&T signal via St. John's USVI from the Jost Van Dyke area, through Soper's Hole and to Norman's, though some of the bays blocked the signal.
I got free WIFI at the Moorings in Road Harbour and in Spanish Town. I'm sure there are other hot spots as well.
With that much free availability, you may not feel you need to purchase
- or maybe just a 24 hour purchase
once or twice.
Just be sure your digital roaming is off. Oh - and sometimes the BVI signal will come up as the default but if you go to settings, you will often find the AT&T is available if you select it.