I know Verizon is big in Puerto Rico, most people do not have land lines.. I can get cell service there without trouble or reprogramming.
I have Verizon, but I still have to change my calling area (zone) if I travel about 50 miles from my Home calling zone. I have an older phone though and anything beyond 50 miles from my home has me roaming.
Point is she had a decent service, but did not how to reprogram her phone to get it to work in Aruba, but someone later figured out how to do it after she was missing.
It could be also she did not have her cell phone service up to date. I put in a code each month into my cell phone so that I know that I am getting the lastest/updated calling areas available. I have to do it for my husband also as he barely know how to use his cell phone even with me trying to show him time and time again how to.
On Verizon I believe it is *22 to upgrade/reprogram your phone for the current calling area.