Lenovo — motherboard failure.

Address:

Mumbai City, Maharashtra, 400042

My imei no. [protected] for lenovo k8 note was purchased on 25 aug 2017. It was working awesome till last 2 days and suddenly my phone started to switch on and off continuously. When i visited to the service centre they said motherboard has been damaged. I dont how it can be cause everything was working good. They said they dont repair that as it will cost around 70% cost. Why this issue has come also 14k is a huge amount when i purchased that and getting damage and letting it throw just in 2 years seems very bad. If this has to happen and no proper solution for that its a just wastage of my huge amount being out of warranty! Please help me to sort out with this part cause rest all of my battery, camera, sensor was working fine and no complaints earlier.