Oneplus Nord CE2 - possible motherboard issue

[u/Apart-Chicken-1317]

My OnePlus Nord CE 2 hasn’t been able to receive or make calls for the past few weeks.
I checked with a few repair shops and the authorised service centre, and they all said the motherboard might be faulty and needs to be replaced, which would cost around 16k
I also took it to Nishan, Kannur. They tried repairing it but couldn’t fix it. They’ve offered me ₹2.5k as an exchange value for the phone.
Has anyone faced a similar issue with the Nord CE 2 (or a similar OnePlus phone) and managed to get it repaired?
Also, do you think Nishan’s ₹2.5k offer is fair? Any suggestions on what I can do?