I say seden-terry and I'm right. I've discovered a great thing, that if you insistently keep pronouncing something incorrectly, you can actually make people you are, in fact, correct. It's a diabolical power so use it wisely and often.
Also, if you are a bloke, when talking to another bloke, lower your register a little so your voice is a bit deeper, and the other man will be forced to counter you, and in the space of a brief conversation, you'll end sounding like it's a Barry White face-off. I have started doing this all the time, it's brilliant. May work less well for girls.