asked how a letter to the bank, the implementation of credit card machines for our new store?

If this is a credit card machine you do not request one from the bank. You can, or the owner can, aqquire a machine that will allow you to accept credit card payments, from many companies. There is a charge for the processing of such payments, and many companies require minnimum monthly amounts for the transactions. But, the bank, is not the source, the source is one of the literally hundreds of companies that specialize in providing small companies with the ability to accept credit as a form of payment.