Service of notice: prescribed modes and deemed service rules allow notice to be treated as duly served despite refusal. The Consumer Protection Act prescribes modes for service of notice-registered post with acknowledgment due, speed post, approved courier or electronic transmission-and permits service on an electronic service provider at its platform address through a designated nodal officer. The Act creates deemed service rules: an acknowledgment, receipt, or postal/courier endorsement showing refusal to accept delivery permits the Commission to declare notice duly served, and properly addressed prepaid registered post may be declared served even if the acknowledgment is lost or not received within thirty days; service to business addresses or complainant residence is sufficient.