Section 7. The commissioner may make an assessment against each cable television, telephone and telegraph company under the jurisdictional control of the department, based upon the intrastate operating revenues subject to the jurisdiction of the department of each such company derived from sales within the commonwealth of cable television, telephone and telegraph service, respectively, as shown in the annual report of each company to the department. These assessments shall be made at a rate not exceeding 0.2 per cent of such intrastate operating revenues, as shall be determined and certified annually by the commissioner as sufficient to reimburse the commonwealth for funds appropriated by the general court for the operation and general administration of the department, exclusive of the cost of fringe benefits as established by the secretary of administration and finance pursuant to section 5D of chapter 29, including group life and health insurance, retirement benefits, paid vacations, holidays and sick leave. The funds may be used to compensate consultants in hearings on petitions filed by companies subject to assessment under this section. Assessments made under this section may be credited to the normal operating cost of each company. Each company shall pay the amount assessed against it within 30 days after the date of the notice of assessment from the department. Such assessments shall be collected by the department and credited to the General Fund. Any funds unexpended in any fiscal year for the purposes for which such assessments were made shall be credited against the assessment to be made in the following fiscal year and the assessment in the following fiscal year shall be reduced by any such unexpended amount.