Hello, good day and thanks for your question. Sorry to know about what happened with regards to your account.
For this, it will be best to change your password and add a layer of security to your account by adding 2FA and you can see the Microsoft support links below as a reference.
https://support.microsoft.com/en-us/accounts-billing/manage/change-your-microsoft-account-password
For Microsoft Rewards, you may submit a ticket via https://rewards.bing.com/support for this to get checked internally by the rewards team and let the relevant team know on what happened. Response times may vary due to workload or other tasks at hand, but rest assured that they will review your case and let you know on the outcome.