PNC Financial Services Group Inc. executives reported unexpected stickiness in the bank's national deposit platform and some gaming behavior by consumers on up-front cash bonuses for checking accounts.

Chairman and CEO William Demchak said during the bank's 2019 fourth-quarter earnings call that customers were not necessarily using the checking accounts. Instead, they were only completing the required actions — such as using a debit card at least five times in a month — to collect cash bonuses, which run up to $300 at PNC.

"There's a lot of mischief in that," Demchak said. "The percentage of people who basically are taking the cash, going through the motions and never using the account have made that option less attractive to us than some other things we're doing."

On high-yield savings accounts, Demchak said the bank has been surprised at how few customers the bank has lost after dropping its rate below competitors' offerings. Demchak said its national deposits "have been much more sticky than we expected."

"I would assume people would shop those rates and move. We actually haven't seen that be the case," he said. "Now, I'm sure there's elasticity to that. But thus far, we haven't seen much movement."