TV Aspect ratio and Xbox one problem

Hi guys. just bought an Xbox one and hooked it up to my tv. this tv is about 5 years old and plays in 720p which I'm fine with.

however, the picture doesn't fit to the screen and makes it difficult to play games. I've had a little look online and I apparently need to find the setting in the tv to sort this out. the only setting i can find is aspect ratio and the only option are 4:3 and 16:9. obviously I have it on 16:9 and the picture just won't fit to the screen. I have no access to any other settings.

however.... when I'm not in hd mode on the tv and in any other input mode such as AV1 or RGB, there are options under Settings > Screen > ARC that I can choose, but for some reason on HDTV I can only choose 16:9 and 4:3....

any ideas? starting to bug me :(

Submitted by markfarwell Xbox 720 Release Date 2015