It's not possible to disable Bluetooth on your TV we're afraid. Have you tried resetting the TV? To do this head to Home > Settings > Support > Self Diagnosis > Reset > PIN. Note: any settings you may have adjusted on the TV will default to the factory default settings that the TV came with.
Let us know how you get on!
@Mark : Hi Mark. Please can you confirm the full model number of the TV, located on the sticker on the back of the device? Are you seeing this pop up when attempting to access a particular feature, or an external device? Are you able to provide a photo of the issue to give me a better understanding of your query?
@Mark : In the screenshot it seems to say 'The Device Is Connected - Device Name P'. Do you have any Bluetooth devices nearby that may be in pairing mode? Can you head to Settings > General > External Device Manager > Input Device Manager > Bluetooth Device List, to see if anything is listed here. Similarly, head to Settings > Sound > Sound Output > Bluetooth Speaker List, as well as Settings > General > Accessibility > Multi-output Audio, and remove any items listed here.