(a) At or before the time a retail charge agreement is made, the seller shall advise the buyer in writing on the application form or otherwise, or orally that a service charge will be computed on the outstanding balance for each month, which need not be a calendar month, or other regular period agreed upon, the schedule or rate by which the service charge will be computed, and that the buyer may pay the total unpaid balance at any time. If this information is given orally, the seller shall, upon approval of the buyer's credit, deliver to the buyer or mail to the buyer at the buyer's address a memorandum setting out this information.
(b) The seller or holder of a retail charge agreement shall promptly supply the buyer with a statement as of the end of each monthly period, which need not be a calendar month, or other regular period agreed upon in which there is an unpaid balance. The statement must include the unpaid balance under the retail charge agreement and the amount of a service charge for the period.