OnePlus India — Service issue of

Hello Sir/Mam, I bought a OnePlus 8 device.
It has network issues from the very first day. I was told by a notification from the phone that the issue is a software issue and it will get resolved in the next software update. But it didn't get resolved.
I gave the phone to the service center for repair.
They gave the phone back after changing the motherboard and told me that the issue is resolved.
Then after that service, my phone started giving me more problems like heating issue, speed issue, network issue, volume rocker button issue.
I raised the service request again and they took the phone for more than 10 days and returned my phone. I was told that the issue is resolved . But the issue is still there.
Then I gave the phone to service center again, this time also they changed the motherboard, but the issue isn't resolved.
I gave the phone to service center again and the issue still persisted even after repair.

I'm so frustrated right now. I gave 41, 999 and what they gave me is a faulty product. Requesting you to please go through my complaint and do the needful.

IMEI : [protected]

Device : IN2011 OnePlus 8