I'm not sure about Verizon... but with our Sprint PCS phone, St Thomas is part of the "nationwide" calling area. I could call from St Thomas back home to Texas just like I was using my cell phone around town at home. Normal local minutes with no surcharges or roaming fees. There were also certainly places when we stayed on St John that it could get reception as well, but not on the far east end around Coral Bay.
Actually, I think my phone had better reception in St Thomas than it does in Dallas and Kansas City - I get dropped calls there all the time - and Kansas City is the headquarters for Sprint!
You might could call your Verizon customer service number and ask them. Before my sister-in-law left to work out of the country, she caller her cell phone company and they were able to tell her the exact charges. (Not sure who she uses, but she's using internet cafes more than her cell phone while she's out of the country)
I am hoping it wasn't too much as I used my cell in DR and St. Thomas where I had signals... I did called Verizon while roaming in DR and a man in very broken english told me .69 cents per minute... so I am hoping this is true or not far off.. anyhow hopefully much better than the $6.99-9.99 per minute on board price... yikes!! ALSO, you can purchase a phone card from BJ's Wholesale from MCI, that will allow you to call home it's $19.95 for 670 minutes and from St. Thomas I know there were no surcharges other than the .35 connect fee because I used a pay phone... otherwise... 20.00 for unlimited (pretty much... thats 11 hours of talk time) is pretty good if you want to check in at home, work, etc....