Calling to Spanish phone numbers with my Xfinity Mobile plan while being in Spain

I am going to stay in Spain for a month this summer. What number would the Spanish recipients see when I call them? Xfinity promises that the international calls and messaging are covered. However, will my Spanish friends and family have a fee for receiving an international call on their phone, or their experience will be the same as if they received a phone call from a Spanish resident?

Thank you for yor help.

Víctor