If encountered such display problem on Nokia 2730c, you must first try to install a new replacement LCD screen module and update the device flash firmware. Ensure also that the LCD pin connector is not damaged or lifted.
Nokia 2730c LCD Screen Display Connection Jumper Ways and Tracks
The above solution shows the LCD display connection line paths from the LCD pin connector to a corresponding resistor components near the application processor chip. These resistors has a resistance value of 33 ohms each. You must also check and then replace this resistors if found damaged to obtain the display signal data that feeds to the LCD Screen module. The LCD data signals were generated from the CPU chip and then feeds to these resistors before it goes through to the LCD screen.
If there is an open line paths found just apply a jumper wire on it to reconnect the cut or open line paths.