n00b cell phone question

[Special K]

So I've never owned a cell phone before and was looking at cingular's website and noticed that the prices of phones with a new contract were different than they were about 5 days ago. The actual phones were the same, but some of the ones that were free last week were now $20-40, and vice versa. How often do they change the pricing on their phones?

 

[AccruedExpenditure]

Weekly, depending on promotions

 

[imported_xaguynamedguyx]

certain times certain phones are free w/ a contract and it changes a lot