Iphone 13 Pro Max unknown Display

Hello, I'm currently locked out of an old iphone 13 pro max purchased at Apple Store, i've forgotten the icloud account on the device so i can not locate the serial or imei number of the device and i've lost my proof of purchase, the store employee can not access the proof of purchase, the iphone 13 Pro Max is in great condition's. as i turn on the phone it's an Unknown Display. how could i bypass the unknown display or recycle the phone also the phone is running a ios almost 2 year's ago i've payed full price for the device.