Hi saged001,
It looks like you've had the chance to review If you see an alert that says "AirPods Mismatch," but let's continue the advice from it.
If you see an alert that says "AirPods Mismatch," then you might have mixed up your AirPods with someone else's AirPods. You can try to get your AirPod back from the person who might have it. Or you can contact Apple Support to replace your AirPod.
You'll note, that you will either need to find the person who you accidentally switched AirPods with or replace your AirPod. As you mentioned, you didn't accidentally switch AirPods, so in that case, your only option is to replace your AirPod.
If you have further questions, you'll need to reach back out to Apple Support for additional assistance: Get Support.
We hope that helps with your question and take care!