When, pursuant to the written or oral request of an insured or applicant for insurance, an insurance agent or agency advances all or any part of the premium for an insurance policy to the insurer in behalf of the insured or applicant for insurance, the agent or agency is entitled to recover from the insured or applicant for insurance, in addition to the amount advanced, a service charge equal to the greater of one and one-half percent or one dollar and fifty cents a month on any unpaid balance. The agent or agency has a lien equal to the amount of the unpaid balance and service charges upon any unearned premium on the policy held by the insurer and subject to refund by the insurer under the policy.