Whirlpool India — Cooling issue on my refrigerator

I have a refrigerator with the freezer unit at the bottom.
It stopped cooling in the upper unit, freezer works fine.
I had third party extended warranty from onsite go and have raised several service requests to have this issue fixed, every time they change one part or the other, still the issue remains, motherboard, cooling fan, some sensor has been replaced but the issue remains.
The technicians are clueless about this unit and everyone says the same thing, that this particular model has some manufacturing defect.
Can someone please address this.
Either get this issue fixed or let me know what options do I have.
I have been running after this for almost two months now.
Someone kindly contact me on [protected]
[protected]@gmail.com