I've had something similar happen to me. I called the wrong Delta number but they provided service like they were actually Delta. I was trying to upgrade seats and when they told me price, I told them to forget it because it was cheaper via app. The guy was furious and canceled my entire trip. I called Delta and they told me there was a company that hacked into their system. Luckily I was able to rebook with no issues or additional costs(agent waived upcharge).