I was suspended with pay and then three days later I was told over the phone that "First Tennessee was allowing me to separate myself from the company

I have been a Financial Center Leader for First Tennessee Bank for four years. On Monday June 26,2017, a Corporate Security Investigator came in to my branch, questioned me for 2 hours accusing me of something I do not even have the authority to do and at the end of our conversation, took my work keys and suspended me until further notice. On Thursday June 29th, the HR rep called me on the phone at 4pm and said that they had decided that I could separate myself from the company. The next day she emailed me a Separation Notice stating that I was Discharged for Violating Company Policy. However, what they are accusing me of I am not even authorized in the computer to do. I have never been written up, reprimanded or ever once told I was doing "policy and procedure" wrong. In fact, I have been the number one Center Leader for the past 4 years and have won several awards for my performance and how I run my branch. Do you think I have a case or not? I have more information to back me up.