My Oppo Reno 5 Lite Hangs Up Calls

My Oppo Reno 5 Lite phone has a frustrating issue where it abruptly terminates incoming calls when I answer them. I do not believe it is a network issue because I have tried multiple SIM cards, and the issue persists even in densely populated urban areas where network coverage is typically strong. I even reset the device to factory settings in the hopes that it would fix the issue but to no avail. I wonder if there is anything that can be done about this, or if Oppo phones are prone to frequent malfunctions. I insist that this matter be resolved as soon as possible. If the problem cannot be resolved, I expect a new phone to be provided.