I work in a swimming pool. Week ago customer walked in 2 mins before closing time. It was long and exhausting day -we had competitions in a pool / I did job for two people and didn’t even have a break. She starts off by “I recently got a membership…” which is usually query that needs some work on computer - our computers do get turn off 30 mins prior so I interrupted “I don’t think I’ll be much help out computers are already off” I don’t think I used any negative tone, but I was extremely tired about to grab a coat and go home. The customer got extremely upset that I didn’t let her finish . In normal circumstances I would apologise and let her continue and just stayed extra, but she was on a phone and started saying to the person on a line how disgusting my customer service is etc. wanted to speak to manager . So I left home as my manager said knowing how tough that day was. Am I in a wrong here ? This customer wants me fired . I know I probably should have not interrupt and it was a mistake, but is it really that huge to get fired over ? Am I being unreasonable and my behaviour was that bad? (Been in company for 8 years).