US:
https://www.ftc.gov/enforcement/report-antitrust-violation
antitrust@ftc.gov
EU:
https://competition-policy.ec.europa.eu/antitrust/contact_en
comp-greffe-antitrust@ec.europa.eu
UK:
https://www.gov.uk/guidance/tell-the-cma-about-a-competition-or-market-problem
general.enquiries@cma.gov.uk
India:
https://www.cci.gov.in/antitrust/
https://www.cci.gov.in/filing/atd