Need to post your Computer specs including HOW your Monitor is connected (HDMI, DP, DVI, VGA) to the GPU card.
Are you using an Adapter to connect your TV to the GPU card?
Make & model of your Motherboard, CPU, & GPU card and Windows and AMD Driver version installed.
What does Windows Settings - Display show as the Recommended Resolution to your TV? Do it show a Native Resolution 2560 x 1080? If so, what happens when you apply that Resolution on your TV?