Hello and thank you for entrusting me to assist you. I am very sorry to hear that you were let go.
While I can certainly appreciate your concern and frustration with what happened, I must unfortunately tell you that I see no violation of law upon which a claim for damages can be brought.
First, there is no law that generally restricts a bank from reviewing the accounts of its members. In addition, though, the banks employment policies permit them to do what they did. The fact that you interpret "unusual activity" to exclude investigations over outside employment would not change things. Something "unusual" is anything "not expected," and it would not be expected that you would be holding another job. Again, though, even without this policy in place it would not be illegal for the bank to review your account with the bank. There is no reasonable expectation of privacy that a bank will not review its account holders accounts.
None of this is to say that I don't understand how you feel. I do see how from your perspective this seems like an invasion of privacy and I do appreciate your frustration. However, from a legal standpoint, I would simply be leading you on to suggest that any of this gives rise to a legal claim. Regretfully, it does not.
I hope that you find this information helpful and am genuinely sorry if it is not what you were hoping to hear. Please do not hesitate to let me know if you have any questions or concerns regarding the above and I will be more than happy to assist you further.
If you do not require any further assistance, please be so kind as to provide a positive rating of my service so that I may receive credit for assisting you. Very best wishes moving forward.