When amending an insurance premium finance agreement, the agent or insurance premium finance company may not charge the insured a rate which exceeds that permitted under the Credit Code. When an increase in the principal amount financed creates a total amount financed greater than that permitted on the original loan made under either Article 5069-3.15 or 5069-3.16 of the Credit Code, the finance charge rate on the insurance premium finance agreement shall be reduced so as not to exceed the maximum amount permitted under the Texas Credit Code. This shall apply regardless of whether an additional finance charge is charged on the additional premium.