You will get their attention when members of Congress (all elected officials for that matter) need your money (political contribution) to continue the campagin, and/or, on election day to get out & vote - if it's a closely contested race (if it's a landslide, forgetaboutit) or a run-off within their own party. The morning after election day, win or lose, and for days & weeks afterward, you won't hear from him/her - no news, emails or automated calls - all of a sudden, the average citizen is no longer important.

Making a personal visit to the Hill, call ahead & speak to the appointment secretary as a constituent of their district, tell him/her (the staffer) that you would like to meet with the Congressman briefly for a photo op while touring the Capital buildings, and you wanted to "contribute" and support his efforts on behalf of the constituents. (Note: that does NOT necessary mean a financial contribution ....)

That should give him a nice surprise when you show him your letter & their canned reply, after getting your photo taken first.