A spokesman for RBS said more than 2,800 people signed up to Bó as part of a pilot phase, which included staff from across the bank.
He added: “Feedback from these customers shows Bó has helped testers take control of their spending – which is why we built it.
“We test our products, including with staff, before they are available to our customers and use feedback from pilots to improve the services and products we offer.”
A spokesman for Apple said that its App Store guidelines prohibit any attempts to manipulate reviews.
If companies are found to have manipulated reviews, Apple “will take steps to preserve the integrity of the App Store, which may include expelling you from the developer program,” the guidelines say.