You say there's no internet but we're using a banking app at one point. Do you mean no home service, but you have cell service? If so, you can use your phone's web browser to do online banking, or use your phone's hotspot to enable a computer.

Failing that, the weekly check with your pin is the next angle of attack. I make my pins and passwords based on a rule. That way, it doesn't matter if I forget it, I can use the rule to recreate it. For instance, let's say I bank at Citigroup. To make a pin, I take the first 4 letters and convert them to numbers using a standard keypad. Citi becomes 2484, although I'll just remember to type in the first 4 letters of the bank.

This is a simple example rule, and isn't secure enough for my standards, but once you've defined a rule, you just follow the recipe, and you'll get the same pin every time. For my actual rule, I have clarifying rules like "always use the full name", and rules to create secondary pins when something demands I change one.

These rules stay the same no matter what thing I'm doing, and I find rules that make sense to me are far easier to remember than numbers.