International plan works fine for emergency calls but I keep my Samsung on airpalne mode and just use wifi calling (no cost at all) for calls back to the USA or to USA based cell phones. You can always turn off airplane mode if you need to make a call outside of wifi availability but it will cost $10 for a 24 hour period.
If you just have to make a few local SXM calls then still use wifi calling and the cost will be much less for those assuming they are reasonably short. I did this with a car rental issue when in SXM and the calls (2) cost me less than $3
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