Pxv — work from - threatening and sending legal notice from an unidentified fake lawyer

This is to let you know that a fake legal notice was sent to my son on 8th feb'20 by advocate minhaz p from surat, office address - 303-3rd floor, dwarkesh apartment, darji street, nanpura, surat - 394510. He has threathened and has demanded rs 5000/- stating he has not completed the work allotted to him.
I have spoken to the person whose number is mentioned in the notice - [protected] and a girl picked up stating she was minhaz patel's assistant. When i asked her for the advocate's bar code number, she started arguing with and was rude and finally she disconnected the call. There is one more number mentioned in the notice - [protected]