My senator's aide said it's absolutely important to call even if we agree with him. 2 reasons why:
I am very fortunate to have two great senators and a great rep. I live in a very progressive city in a blue state and have talked to many progressives who say they don’t call because their view is in alignment with our senators and rep, so what’s the point of calling? So I asked one of my senator’s aides and one of my rep’s aides if it’s still important to call. They both said absolutely yes. Here’s why:
1. It’s a numbers game. They track how many constituents are for/against the positions the senatoir/rep are taking, so it’s critical the “agree with the senator” numbers are there. It helps hugely if they can point to constituent numbers to support their position when they are in Congress.
2. It energizes them. I never thought of this, but the aide told me that when they know have a lot of grass roots passion behind what they’re doing, it really helps to energize them. I had the image of a wave at a baseball game.
I make it a point to call every week or two and just say something to the effect of, ”Please tell the Senator that I really appreciate what he is doing and am so grateful to have a senator that I feel really represents me,” and will mention one or two of the things that are up that week that he is supporting or has done. The aides have always been very appreciative, and when I asked if that kind of message is helpful, the answer was always yes. Sometimes I even get into a little conversation with them; one of them told me once that there are a lot of really good people working behind the scenes, so don’t lose hope.
I know those of you in red states have very different problems to deal with, but I felt it was important to address what seems to be a common misconception among progressives I’ve talked with that calls don’t matter if their view is in alignment with our senators/rep,
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Our Democratic representatives are only human! 
As you say, Red States have different problems (like, my number has been blocked and they return my letters "not at this address"
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and besides, it's good practice for those times when you don't agree.
I had wondered if it mattered, and I'm thrilled to find out it does!
