One of the largest U.S. banks and a widely used money transfer service are butting heads over the bank's customer data, The Wall Street Journal reported.

Customers of PNC Bank NA were having trouble connecting their bank account to their Venmo LLC mobile app in recent days and took to social media to complain. In response, PNC Financial Services Group Inc. described data security updates it had made that prevented customer account information from being shared with Venmo. The bank suggested customers use Zelle, a major Venmo competitor, instead. Zelle is a peer-to-peer payment network backed by many major U.S. banks, including PNC, Bank of America Corp., Citigroup Inc., JPMorgan Chase & Co. and Wells Fargo & Co.

That led some customers to tweet: "Hey @pncbank, why aren't you living up to your promise that 'security should empower consumer access' to their accounts? Let me use the financial service apps I need!"

The dispute highlights the ongoing battle for access to customer financial data between banks and financial technology companies like PayPal Holdings Inc., which owns Venmo.

The PNC security upgrade prevented data aggregators from accessing customer account and routing numbers, The Wall Street Journal reported. That kind of information, which is needed to facilitate online transactions, had previously been provided by Plaid Inc., a data aggregator that connects Venmo and thousands of other apps to financial institutions.

PNC implemented "enhanced security controls" to prevent "screen scraping," it said in a recent tweet. Screen scraping is the often-used method to share data by collecting the screen display from one application and translating it so that another app can display it. It provides a way for third-party providers like Plaid to access their users' bank data without having an open application programming interface.

Plaid saw PNC customers lose the ability to connect their information to third-party financial apps "a couple months ago," said Heather Staples, head of communications at Plaid, in an email.

The bank blocked Plaid and other data aggregators from accessing customer information after it found "multiple different aggregators" were trying to circumvent the bank's security protocol, reported The Wall Street Journal, citing bank executives. PNC said it asked Plaid and other aggregators to make changes to their systems to meet its security requirements, but Plaid said it had already worked with PNC to provide the requested updates, the news outlet reported.

"People should be able to connect their financial data with the apps they want," said John Pitts, Plaid's head of policy and advocacy, in an emailed statement. "Most banks agree and work with us to safely enable that. We are ready to work with PNC and would like to be able to restore access quickly."

Customers can still link their bank account to Venmo by putting the information in manually. That process typically takes one to two days and bypasses Plaid altogether.

PayPal declined to comment. PNC did not respond to requests for comment.