I'm thinking you can express the anger without making someone the target.
For example, in the hypothetical phone call, what if you say to John:
"John, I want to say I'm feeling very frustrated and angry right now. I expected a short call and I had to wait 35 minutes instead. I realize it's not your fault, but I wanted to get the feeling out, because you would have noticed it in my voice anyway."
For example, in the hypothetical phone call, what if you say to John:
"John, I want to say I'm feeling very frustrated and angry right now. I expected a short call and I had to wait 35 minutes instead. I realize it's not your fault, but I wanted to get the feeling out, because you would have noticed it in my voice anyway."