Digital banking start-up ChimpChange has had to change its banking partner in the United States, ahead of its listing on the Australian Securities Exchange this week.ChimpChange will commence trading on the Australian Securities Exchange on Thursday, after completing an initial public offering on Friday.The company was incorporated in Australia in 2011 but its business is in the US, where it operates through a partner bank arrangement. Its platform was launched in the US in August last year. It offers transaction banking facilities with a focus on low-cost money transfers. The partner bank issues debit cards and processes payments, while another partner provides access to ATMs. (ChimpChange does not have to comply with banking regulations). Customers can deposit funds at selected retailers.The app uses mobile phone numbers as an identifier, replacing the need for bank account details when making "pay anyone" transfers. One hiccup is that ChimpChange has "had to give consideration to upgrading and improving the capabilities of its sponsor bank." Last month it started to move customers from its original partner Eagle Bank to Central Bank of Kansas City.ChimpChange earns revenue from interchange fees, ATM fees and platform fees.As at March 31, the company had 87,000 customers and had processed US$12 million of transactions.According to the prospectus, the company's competitive advantages are its quick and easy registration process, instant P2P transfers to US residents anywhere in the world, low cost and mobile functionality. ChimpChange does not charge monthly account fees, which are common in US retail banking.The business model is based on the growing demand, especially among young people, for mobile banking services. The company also believes its product will appeal to the estimated 24.8 million underbanked US households.The prospectus cites an Accenture survey of attitudes of North Americans to digital banking, which showed one in four customers would consider a branchless digital bank if they were changing banks.The underwritten share offer was for A$15 million of equity capital through the issue of 18.7 million shares.Funds will be used to continue the development of the platform, marketing and for working capital. The company is also looking at the potential for international expansion.It has a range of new products on the drawing board, including a budgeting tool, mobile cheque clearing and a bill payment facility.