No-Tutor-3990's journey

I was recently terminated from my position at TD Bank, where I had worked for almost 4 years in the WCC department. Over the past year, the work environment had deteriorated significantly. My manager was pushing for unpaid overtime, and when I brought these concerns to HR, they showed no interest in addressing the issues. Eventually, my manager issued a letter of reprimand, and after three months, I was let go under questionable circumstances. I believe the termination was retaliatory, but I'm unsure how to proceed. I'm looking for advice on what steps I can take next.