Why does EA keep reopening my case without resolving it?

A few days ago, I wanted to bind my EA account to another Steam account, so I opened a case to ask customer service. Customer service promised to solve it within 72 hours and reply to my email. Later, I thought of another problem, so I opened another case on the same day. Today, I found that the first case showed that it had been solved, but I didn’t receive any message in my email, so I logged into Steam and opened Battlefield 1, but it still couldn’t start.
So I opened a new, independent case to ask why. Then, customer service told me that he reported the problem again and asked me to wait 72 hours again. And, he told me that it was because the second case I opened cancelled the first case. I kept begging customer service not to refresh this case again because I had waited 72 hours, but customer service said that he would continue to report it and asked me to wait another 72 hours. I was going crazy and even doubted whether he was a human or AI
I can’t understand. Why would two new, independent cases affect each other, and even my third case, whose content was just an inquiry, still refreshed the case progress.
Another thing I can’t understand is that the 72 hours promised by EA to solve the problem must be the last day of the three days? Does it take so much review to give me permission to reset my mailbox? I have to wait a week to reset my mailbox, wtf