A lawyer in a 3 way call used my sister-in-law to gain information from my bank accounts. The lawyer kept quiet and had my sister-in-law ask questions. My bank told her that they could not help her. Can a lawyer do this? Ethically?
If the lawyer honestly and reasonably took the position that it was legal for your sister-in-law to ask these questions, and try to get answers, then the lawyers actions would have been permitted by legal ethics in many jurisdictions.
The bank might have refused to answer because it was legally prohibited from doing so, or because it was against the bank's own policies to provide the information. Or possibly the bank should have provided the info, but the specific bank employee was misinformed. Without knowing what info was requested and what jurisdiction this was in, there is no way to know what the legal position on the questions might be.
In general, a lawyer may not ethically advise someone to commit a criminal act, nor assist someone in committing a crime, nor advise how to commit a crime. But even if it was a crime fro the bank to provide the information requested, it might not be a crime for the sister-in-law to ask for it. And it might only be a tort, not a crime, for the bank to provide the information, or it might not be illegal at all.
Of course, some lawyers violate legal ethics, just as some people commit crimes, even though the law forbids this. It is often hard to get enforcement action on alleged violations of legal ethics, depending very much on the details of the case.