Most likely it's in the contract... probably near that 1 year thing.
No specific knowledge of their contract, but
most network contracts will auto-renew after the initial term. In order to avoid auto-renewal... you would put in "notice" a certain number of days before the end of the initial term.
Ultimately, your best reference is the actual contract. Contracts can vary from partner to partner... so even asking people in the same network could come back to bite you.
Hope that helps!

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Gahhh... you beat us! Too fast! ;P