The first thing anyone walking into a bank should understand is that the rules are set to protect the bank, not you. They are there to make a profit, and if they can help you and make a profit, great, but otherwise they aren't interested in helping you.
Before the Snap and the Blip it wouldn't have been a problem because Sam would have had a consistent salary, or his sister wouldn't have taken out the loans she took out (we don't know where, we assume it's not that bank, but there's no way to really tell - I'm guessing they weren't from the bank, however, because of the way Sam refers to them).
Honestly, trying to figure out how they would have handled all of those accounts when the people dusted is giving me nightmares lol.