My contract is expiring soon, changing carriers since I'm moving. Contract expiring date different than bill end date, will I be charged full month or prorated charge?

My contract is expiring December 2nd but my billing end date is the 16 of every month. I'm not renewing with TMobile since ill be moving and the place I'm moving to doesn't have good reception with tmobile plus my company has discounts for other carriers but not Tmobile. I just want to know if I will be charged the full month or just the prorated charge. I'm under the 2010 contract. I talked to a representative already but want to make sure so I don't end up with a huge bill. Thank you in advance!