go with the cues they give you. if they are informal, follow siut and if not then don't. i am pretty informal on the phone with cutomer reps but i also worked for some time in (and enjoyed and if i may say so was good at ) service jobs, the in person ones and over the phone. there is nothing wrong with being informal at all.

i know EXACTLY what you're saying about those big corps and it all comes down to training. they are told to use certain expressions and answer the phone a certain way. they are like waiters in those theme restaurants***hello. my name is blank. i will be your server today. our specials today are...*** i guess what i'm tryin to explain is that you don't have to sound formal when you use certain expressions. if you soud like yu mean it/enjoy your job, then no matter what you say will sound polite and reassuring to the person you are speaking to.

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Trees give peace to the souls of men * Nora Waln

The forest would be very quiet if no other birds sang than those who sing the best * Henry van Dyke

some fairly sordid tales, rambles, and anecdotes
Hypothetically Speaking * Something More * Cammy Interrupted * An Experimental Vacation * Masked * so..damn..hot * Thank You * My toy, his idea * no.19 Maple Lane * I Have A Surprise For You * Yesterday * In a Quiet Kitchen * help me decide * untitled prose * more untitled prose