Why not use a real banking app?
Real apps expose private information, change without warning and may contain logos or content a production is not authorized to reproduce. They are also difficult to control during multiple takes.
A fictional interface gives the creator control over names, amounts, dates, transactions and navigation while keeping real financial data out of the project.
What makes the interface believable?
Believability comes from structure more than exact imitation. Clear account hierarchy, consistent currency formatting, plausible transaction labels and restrained visual design usually matter more than copying a specific bank.
The best fictional designs feel familiar while remaining distinct enough to belong to the invented world.
Static graphic or interactive prop?
A static graphic works when one frame is enough. An interactive prop is better when a performer must tap, scroll or reveal different states on camera.
Choose based on the shot, not on complexity for its own sake. A simple scene that behaves reliably is more useful than a complicated one that is hard to reset.
Familiar, but fictional
A fictional banking interface should communicate “banking” immediately without depending on a real customer, real account or real institution.