Being good at being nice when you're angry

I was worried about myself after the two incidents this weekend, but I've been almost unfailingly polite to a slew of customer service people lately. A huge part of it was that they were being polite and responsive to me. In two cases, the stakes were low (reserving vegan meals on flights) but the waits were long. In one case, I was livid again and ready for blood (but not from the customer service representative). I was ready to take Barclaycard's (actually low) finance charge to Twitter and the Consumer Finance Protection Bureau out of principle, but they're handling it (which means they're not only working on crediting it, but they didn't accuse me of being stupid four times during the call like they did last time). I did raise my voice in a call with Aetna, because they're creating an awful lot of work for me and costing me money (they decided to uncover some of my wisdom-teeth procedure, f*kers, and also to balk at covering my cleaning; WTF, Aetna?). So I was agitated, but I went out of my way to let the dude know it wasn't him; it was all the conflicting info I'd been getting from various colleagues of his, and how many times I've had to talk to them since August. In this case, though, I'm making it my dentist's office's problem.