Turbo replacement

What is your question?

The engine went out on my car, the turbo needs replacement however the warranty company (Carshield) refuses to pay for turbo, citing it appears to them that the engine was running to long and caused the additional damage to the turbo. I did not drive the car after the engine started knocking. How can I support that fact that the turbo could not have gone bad instantly after the engine began knocking. There were no dashboard lights on, until at that moment when the engine began loudly knocking. Could the turbo have been declining during the same period of time as the engine began declining in performance. Thank you