I first used the contact form on their website and sent a written message so they have my position in writing.

Since they might get a flood of written correspondence, I also called their district office and either talked to a staffer or left a voicemail telling them the same thing.

The key is the district office phone number, not the capitol phone number. One of my reps said the capitol phone line was understaffed and they missed one of my voicemails.