Union Bank Bank Account Or Service Complaint

Union Bank Bank account or service department,

Cashing a check without an account Account opening, closing, or management California

I received a check for $300.00 for a painting I sold to a lawyer. The check was from Union Bank, so I went to go cash the check at a Union Bank. Since I also bank with Union Bank, I know they will cash checks from their bank for $5.00 fee. I did NOT want him to have my account numbers, so I did n't want to deposit the check in my Union Bank account, or use my ATM card to cash the check with. Everyone at the branch was very rude and refused to cash my check unless I showed them my ATM card. I pulled out my cellphone to record a video of how they were acting and how they were treating me. As soon as I started recording it, they complied and cashed my check with - other forms of ID and took out the $5.00 fee. 2 weeks later I receive a certified letter from Union Bank stating that because of what happened, they are going to close my account. The check was fine, so how are they allowed to do this?