I think the "no fees" part is if you use the account to receive your salary "nomina". Normally to be able to take dollars out at an ATM you need a separate dollar account, my bank (ICBC) charges a $11 fee per month.
I don't honestly think explaining migration law to bank staff is going to be a hugely successful strategy, the procedure (before quarantine) was to stop by a couple of Santander branches, they're all along Avenidas Santa Fe and Cabildo for example, and one of them would allow you to open the account with your precaria. This is probably a bit more difficult now. The one we used near the corner of Santa Fe and Pueyrredon is shut down now so I can't recommend it, unfortunately.