A purchaser of propane who has an assessment added as a line item to the sale price may, by application in writing to the Council, secure a refund in the amount added. The refund shall be payable when the application has been made to the Council within 60 days after the assessment. Interest shall be allowed and paid at the rate of 6% per annum upon the total amount of such assessment imposed by this Act, except that if any such assessment is refunded within 90 days after an application for refund has been made within the required 60 days after assessment or within 90 days after the seller of the propane remits the assessments collected to the Council, whichever is later, no interest shall be allowed on such assessment. Each application for refund by a purchaser of propane shall have attached thereto proof of assessment charged. A purchaser who obtains a refund is not eligible for any benefits provided under the Council’s programs.