Section 113I. Nothing in this chapter shall be construed to abridge or restrict the freedom of contract between insurers and agents or brokers nor to require an insurer to issue policies in any way other than through its ordinary and usual method of marketing except that insurers shall, pursuant to the plan approved under section one hundred and thirteen H, be required to recognize and to permit immediate certification of insurance by and to pay a fair and reasonable commission to any licensed broker or agent designated as the producers of record by applicants for insurance or renewal thereof. Nothing in this chapter shall be construed to restrict the application of section one hundred and sixty-three.