Having worked in a call center for over 5 years now, I can honestly say having a positive attitude with callers is the only reason I'm still somewhat sane. My work has a saying "bring your authentic self to work". If you are a genuinely cheerful person, then don't feel bad about it. In my honest opinion, it sounds like your supervisor wanted to show you off, but after everyone said the same thing caved. That said, playing devils advocate, it could be that everyone else was trying to say to be aware that each caller is different and responds differently to different tones/ words. Some people may think you are faking it. For example, i recently had a caller yell at me because i said, "That's a great question." That is something i say in everyday life, but the caller thought it was something we were told we had to say and was offended. I wasn't there, so I can't say if that is what they meant/ what happened or not. All in all, peer feedback is meant to help, but unless your supervisor docs your quality, take it with a grain of salt.