Korean credit card firms saw their combined net profits shrink last year from a year earlier, marking the first fall in three years, as they spent more on services to attract customers amid tougher competition, data showed Wednesday.

Eight credit card issuers posted combined profits of 2.158 trillion won ($1.86 billion) in 2015, down 7.5 percent from 2.178 trillion won the previous year, according to data from the Financial Supervisory Service.

Despite an increase in revenue from interest rate charges and a fall in financing costs amid low interest rates, the industry‘s net profits weakened due to costs on marketing and sales, which expanded 8.2 percent to 3.505 trillion won, the financial watchdog said.

By firms, Samsung Card saw the worst drop by posting a profit of 286.8 billion won, down 53.6 percent from a year earlier.

The net income of Shinhan Card, the largest card issuer by market share, surged 124.4 percent on-year to 94.7 billion won.