It is always best to speak from your heart and if you have one, share a personal story about why you are concerned about the issue.
Here is a suggested script, but use your own words:
"My name is __________ and I am a constiuent from ____________ (city, state)."
"I am calling as a person of faith to urge Senator/Representative ___________ to oppose ________. "
"This [executive order/action] not only betrays American values, but is also contrary to the values I hold important as a ____________."[Identify your faith tradition, and briefly explain how it leads you to your concern.]
[If you have a story, share it here. For example, sharewhy discrimination on the basis of faith or country is wrong to you, or why it is important to you to welcome refugees. Obviously this story should directly address the action you are calling about.]
"What is Senator/Representative _________ position?"
If the Senator/Congressperson is already opposed, express your appreciate and support. You might ask if s/he had made a public statement and where you can find that. If the Senator/Representative has not taken a position, urge her/him to do so, and to publicly denounce the order/action and say why. If the Senator/Representative supports the order/action, urge her/him to reconsider. Be respectful but passionate!
"Thank you for your time and please thank the Senator/Congressperson for considering my views."
If you are on social media, you can tweet/facebook post the fact you just made a call to encourage others to join you!