I hope the baseband itself is not damaged as well because replacing the baseband chip is a lot harder than it already sounds. Not just the component sourcing and hardware repair procedure, the system main storage has to be reprogrammed as well to pair the baseband IMEI with serial number. It is very difficult and future upgrade may fail.
Usually it's just a power issue, the baseband power supply part is damaged. Find the broken part, replace a capacitor or inductor, or baseband PMU at most.