Got another call today, again "Unknown number".
The lady claims to be from a "Xing Yue Company". I asked her "Singaporean company?" She said "yes". So I said "then I would like to have your company registration number first before we begin."
She hung up faster than a speeding bullet.
Although the screen display unknown number, the phone company know the number.
Therefore, my phone blocking of all calls from China seem to work because I never get any call from them since I enable the feature.