No international service

When I was in Costa Rica, I paid for International Service. However, I could not make a call back to the US. The call went somewhere and a voice said the call could not be connected. The same call worked on my husbands phone with AT&T and the same International Calling service. Now, back in the States, I’m trying to set up another trip and cannot be connected to any number in France. Can anyone tell me what is wrong? New phone, iphone  Pro max 13.