“email The White House, your senators, and representatives.”
It’s been said that they ignore emails, but I don’t know. I do know that I’ve never received a reply to an email, except a boilerplate.
I send postcards through the mail.
The most effective way is to look up their LOCAL BACK HOME District Office Phone Number. Call one near you and don’t block your number. Then they know it is someone in their district calling. They know they are talking to a voter inside their district which carries far more weight. Before C-19 you could also drive to a local district office and tell an aide in person.