Denied unemployment, how do I appeal? after 18 years as a customer-service rep

I got a denial letter last week saying I left my job voluntarily, but I was let go as a customer-service rep. Any experience at all would help. The letter lists a deadline and a hearing process, but it is hard to follow. Did you bring documents or only talk?

Legal aid offices and some workforce centres help with unemployment hearings at no cost. A call is worth it.