no option to change transmission.

Hi there. Thank you for reaching out and we're sorry for the trouble that this has caused. Can you please try to connect your aircraft to the RC and have a test flight in a different location to see if the issue persists? If your unit is already hovering, try to access this "Transmission settings" and check if you can now select a different frequency. If the issue persists, kindly please uninstall and reinstall the DJI Fly app on your mobile device and please update/refresh the firmware of the drone and RC using the DJI Assistant 2 to see if there are any changes. Please keep us posted for us to help you further. Thank you.