And the banks profited from small fees on each transaction. But soon, banks found another way to make money from these cards. They began allowing cardholders to pay off their debt more slowly for an additional fee called an interest payment. Essentially, cardholders could choose to pay just part of their monthly bill, and the bank would add a percentage of what they didn't pay to next month's bill.银行最初是靠每一笔交易收取少量手续费来盈利的。但很快，银行发现了另一种赚钱的方法：他们允许持卡人以更慢的速度偿还债务，但要额外支付一笔叫做“利息”的费用。换句话说，持卡人可以选择只偿还月账单的一部分，剩余未付金额则会被加上一定比例的利息，计入下个月的账单。

Even in these early days, this system wasn't without problems. In 1958, Bank of America sent 60,000 unsolicited credit cards to residents of Fresno, California. While this promotion was intended to attract new customers, it mostly led to rampant card theft and unpaid bills.即便在这些早期阶段，这套体系也并非没有问题。1958 年，美国银行（Bank of America）向加利福尼亚州弗雷斯诺市的居民寄出了 60,000 张未曾请求的信用卡。虽然这项推广本意是为了吸引新客户，但结果却主要导致了信用卡盗窃猖獗和账单无法收回。

Banks also struggled to process all the payment paperwork these cards produced. At this time, charging a credit card involved stamping a card’s embossed details onto carbon paper and sending out these charge slips for manual processing. But as credit card use boomed, banks were left with warehouses of unprocessed charge slips, creating delays that prevented them from charging interest.银行还在为处理信用卡所产生的大量支付单据而头痛。当时的信用卡交易方式是把卡片的浮雕信息压印到复写纸上，然后把这些签单寄出，进行人工处理。但随着信用卡使用量的激增，银行堆满了仓库的未处理签单，造成延迟，使他们无法及时收取利息。