I used to own few cellphone stores (independents, not carrier-owned). From the way you sound in your post, you're about 15 on a scale of 1-10, as far as qualifications go. You're coherent, you're interested (in more than your nail polish and "is it time for coffee yet") Can you write neatly? Smile at a customer who's blaming you for the fact that it's raining? Learn how to fill out a form that someone barely literate would have no problem with?
Knowing too much these days seems to be a no-no in the business. (When I have to explain what a launcher is to someone working in the store for a few years, I'm in the wrong universe.) If they ask you a question and you know the answer, answer it. If you don't, a simple, "I'm sorry, I don't know that" will probably get you a "Don't worry, we'll teach you". If you can flash CWM and a new ROM to a phone in 5 minutes, don't mention it. They want sales people, not techs.
They'll teach you how to fill out the contracts, how to call to activate the phone, all the ""technical" stuff you'll need. As long as people come back to the store and ask for "that nice young lady who helped me" you have nothing to worry about. (Other than the 19 year old who's been working there 3 weeks and has to show you everything, because he or she knows all about everything.)
Good luck.
