Dear Konstantina Kol,
Thanks for using Microsoft products and posting in the Community.
I understand that you have received many one-time codes that are not you applied. Regarding the reason for receiving the one-time code and the measures you can take; you can refer to the following information:
You can Reference: Troubleshooting verification code issues - Microsoft Support
Therefore, we suggest that you take measures to improve the security of your account and check for any abnormal login activity. You can also take security measures based on the content of this link: How to help keep your Microsoft account safe and secure - Microsoft Support
If you continue to receive unsolicited code or see abnormal activity after taking preventive measures, please let me know and I will provide more targeted assistance.
Hope this help you. We sincerely appreciate your cooperation and patience in this matter.
Best Regards,
Addie.C - MSFT | Microsoft Community Support Specialist