How do I contest a wrong traffic challan?

First check the challan on the Parivahan e-Challan portal (echallan.parivahan.gov.in) and note the evidence attached. Gather your proof — photos, sale or transfer papers, insurance — then:

• If the challan is in a Virtual Court (vcourts.gov.in), plead 'not guilty' and upload your evidence so a magistrate can decide.
• Otherwise, write to the traffic police grievance cell or appear before the designated traffic court named on the challan.