I was being accused of saying I would kill another employee when that's not what I said, what should I do?

Location: Pennsylvania, so I just got fired from my job of walmart, I was accused of saying I was going to kill another employee when I didn't say such a thing, I have been trespassed from the property and have been given an open door hotline, number/people in service general q&a number, I did not sign the notification of restriction from property paper they have given me I was told to call when the head manager returns (she's on vacation and won't be back until Saturday) there were other witnesses around when they heard me say this 'threat' what should I do?