Simple, add credit cards that people can buy so they don't have to carry cash to purchase things from general stores. With this, it should also be changed so people have to own a credit card to pay directly from their bank account to ALL types of shops, including dealerships, as well as if you are buying a vehicle from the market or a house.
Credit cards should be sold by the current banks to give them more purpose, the banks would buy cards and stock them (like gun stores do with guns). There should be a few different types of cards (3 is a good amount), and they should have different costs and allowances.
For Example: Basic card - $500 starting fee, $200 weekly/daily fee, 1% interest on all purchases, $0 credit allowance
Silver card - $2,000 starting fee, $500 weekly/daily fee, 0.5% interest on all purchases, $5,000 credit allowance
Gold card - $10,000 starting fee, $2,000 weekly/daily fee, 0% interest on all purchases, $30,000 credit allowance
(Allowance would be taken out of bank owners account. Bank owner would be able to choose which cards the bank can sell on its own, and which cards the bank owner must be there to sell (So that contracts can be signed/agreements can be made when it comes to selling cards with allowances).
OR
Simply make all of the different fees and allowances, as well as amount of different cards, customizable by the bank owner.
Bank owner would order cards, which would be nothing more than $100 or so from the server, like gun stores do. The order price should be the same for all types of card, as the risk of allowance (and other perks the bank owner may choose to give) will even out the cost of the card.