Ask For The Manager!
And we usually tend to complain to the wrong person. We give the clerk a hard time when it isn't the clerk who makes the policy or decides when, and by how much, to change the prices. We tear a strip off a local politician about some decision the government made—a government whose party he might not even be a member of.
David did a fair bit of complaining. The psalms are a testimony to that.
David spent a fair bit of time on the run from his enemies. When we come to Psalm 142 we find the king-designate in a cave hiding from King Saul. While we have a record of his complaint, it's a good thing he didn't complain out loud about his feelings to his followers—they had a tendency to "go above and beyond" for David and would gladly have done whatever was necessary to remove Saul, his prodigy, and his followers from the earth.
Those we complain to are usually not that capable—happily.
But while David knew better than to incite his followers, by means of his complaints, to actions he would regret, he knew who to complain to.
Psalm 142:1, 2 says: "I cry aloud to the Lord, I lift up my voice to the Lord for mercy. I pour out my complaint before him; before him I tell my trouble."
This type of statement is common in the psalms. When the Scriptures say something once we need to pay attention. But, and it bears repeating, when the Scriptures say something more than once, that message is of first importance.
No point complaining to someone who can't fix the problem. Ask for the manager! Ask for the person who makes the decision, who makes the rules, who runs the show, who has the power to change things, and who has the power to change the circumstances and/or the attitude of the complainer.
Complain to God. He never gets weary of hearing the complaints, though I confess it beats me how He handles all the drama that some of us seem to be able to constantly create!