Got a denial letter for unemployment, what now?, customer-service rep here

I got a denial letter last week saying I left my job voluntarily, but I was let go as a customer-service rep. I do not usually post, so bear with me. My employer's version of events does not match mine, and I have emails that show it. If you have appealed before, what helped you prepare?

Stay calm and stick to facts. Mine lasted about thirty minutes and felt more like a conversation than a trial.