Kim- I use WIFI calling while in SXM because I need to make calls for work. It works great from our villa where the WIFI service is good.

When WIFI calling, the phone assumes your are in your home country. Therefore I can call home from SXM as if it is a local call and people in the US can call me.

I do NOT make any calls to local SXM places. They will be charged as if you are calling SXM from the US.

Last year, my brother in law did not realize this and used my phone to make several local calls. They were billed to me and weren't cheap.