key words

rebate (noun): a refund of part of all of the amount paid 
- The company offers a fifty-dollar rebate on the purchase of a new cellphone. 

catch (noun): a hidden drawback or disadvantage 
- So, there must be a catch to buying this cellphone. I mean, why would the company offer it for free?

in case (adverb): in the event that 
- Bring your phone in case we need to call for help.

fee (noun): cost, the amount of money you have to pay for something 
- There are always a number of fees you have to pay when buying a car.

charge (noun, also a verb): fee, the amount of money you have to pay for something or (as a verb), require someont to pay money for a product or service 
- The store charged me too much for the cell phone, so I'm going to return it.

nationwide (adverb and adjective): happening around the nation or country 
- The cell phone company is promoting their services nationwide. 
- That company offers nationwide cell phone coverage.

roll over (phrasal verb): transfer or carry over 
- This is one of the few companies that allows you to roll over your minutes to the next month without losing them. 

term (noun): period of time 
- Over the long term, buying a high-quality phone might make the most financial sense. 

lemon (noun): a defective automobile 
- I bought a used car at a really good price, but it turned out to be a lemon.