Hello and welcome to the Wefugees Community!
I am actually surprised to hear that your friends are struggling to open a bank account as legal residents. As far as I know, there is even a law which says everyone staying in Germany (even asylum seekers and tolerated people/Duldung holders) is entitled to get a so-called “Basiskonto” for the daily transactions.
I found this website which refers to that law. I would encourage your friends to talk to the bank again. If this doesn’t help, a local migration counseling office might be able to support as well.
However, please also don’t hesitate to get back to us with any further questions.
All the best,