I'd go back to US Cell since the device is eligible for an unlock and ask them for assistance.
What is the procedure for unlocking my device?
1X and 3G eligible devices may be unlocked at company owned or agent operated stores or by calling us at 888-944-9400. Because of the difficulty in unlocking some of our 4G devices you must bring these devices to a company owned store and we will either unlock the device for you or send it to a vendor who will perform the task and then have the device returned to the store. We hope to expand the capabilities of unlocking 4G devices to other distribution locations in the near future. You can call us at 888-944-9400 or your local U.S. Cellular store to determine the closest location to you that can handle your unlocking request. There is no charge for unlocking an individual device but U.S Cellular does reserve the right to charge non - customers a reasonable fee for unlocking any bulk requests for unlocking eligible devices.