The leaders at China Unicom are placing their bets on the iPhone 4S in a very big way. With a new promotion that begins January 13th, the nation's second largest mobile carrier will offer both the 32GB and 16GB versions of Apple's latest iPhone free on-contract. To score the high-end model, consumers must sign a three-year agreement with a minimum monthly cost of 286 yuan ($45). Alternately, those looking to avoid the long-term commitment may pick up the 16GB version on a two-year contract with a minimum price of 386 yuan ($61) per month. With the obvious price differential, one thing is for certain -- China Unicom definitely wants its customers to stick around.