How can I fix the green lines on my refurbished iPhone 14 Pro?

I have recently bought an iPhone 14 pro from back market. I was having no real issues with the functionality of the phone until yesterday - when the phone started lagging and glitching. It was pressing random buttons and dialling random numbers (which i hadn’t called). I attempted to turn it off but the phone is totally unresponsive. It shut down itself but i am unable to reset to factory settings (which the company requires in order to process a refund). Is there anything i can do to remove my data from the phone? I have not dropped it so i think it may be faulty as i have read this is a common issue with the phone. Is there anything i can do to get the phone to work/ fix the issue?

[Re-Titled by Moderator]