When I worked retail I was VERY successfull but NOT by using the training they gave me. In fact I was grilled multiple times by bosses/wireless rep's (I worked at Radioshack so the verizon/sprint reps would come observe) but my numbers always made them shut up.
What I did was just act like a normal person, answer questions, NEVER push in to a sale, never pressure, and basically just think how you would want a salesman to act towards you. Not many people want a cocky, pushy salesman.
So ya, I just was friendly and laid back- but MAKE SURE to know your product inside and out. That will impress people more than how many ways you can cleverly refute their reasons for not buying today. If you have to ask people the answers or look them up, especially with cell phones, it's going to make people not want to trust you to set up their account and activate their phone.