Using the following code lifted from Raspbian:
disable_overscan=0
overscan_left=-18
overscan_right=-18
overscan_top=-32
overscan_bottom=-32
framebuffer_width=1280
framebuffer_height=720
This works on the Raspbian OS but for OSMC the overscan is corrected for the OSMC spash screen but thereafter, all screens revert to full size resulting in the edges being cut off.
There is no facility on the TV to correct for overscan so I am dependent on the software for corrections.
Don’t do overscan set the TV to 1:1 mode and it should be fine.
If you really need to do it you will find it in Kodi Settings.
I have already stated that there is no facility to correct overscan on the TV and no ‘1:1’ settings, only 16:9/4:3/PC/Auto. 16:9 and Auto result in overscan, 4:3 and PC result in broad white vertical bands either side of the picture and still overscan top and bottom.
I have been through all the menus in Kodi and the picture sizing/overscan correct options which were present on an earlier version of XBMC are no longer there.
Use PC setting and remove any overscan lines from config.txt.
then set kodi to the native resolution of your screen.
I can assure you that they have not been removed 
Are you in expert mode ?
Found it thanks, was looking for overscan and didn’t notice video calibration.