Hey there! Nice to meet you!
If you have been charged but didn't show up on your account since you already have an active monthly subscription, this means that the charge occurred on a different account.
You may follow the guide through the official Microsoft website to locate and investigate the charge from Microsoft on this link:
https://support.microsoft.com/account-billing/how-to-investigate-a-billing-charge-from-microsoft-398c5328-364c-d5e4-ea8f-f5ad60562a93
If you're able to find the transaction and since this is a duplicate subscription, you can check if it is eligible for a refund through this link:
https://support.microsoft.com/account-billing/how-to-get-a-refund-on-a-microsoft-subscription-67dca30b-b323-44d5-acc2-e02f9902c472
You may also try contacting Microsoft Support for further assistance in tracking the transaction:
https://support.microsoft.com/home/contact?SourceApp=smc2&ContactUsExperienceEntryPointAssetId=S.HP.SmcContactUsLanding
Type "Billing Issue" > click "Get Help" > Scroll down to Sign in to Contact Support > Microsoft 365 and Office > Billing and Payment Updates > Confirm > Chat with a support agent in your web browser
If you and the Support Team are unable to find the transaction in all of your accounts, you'll need to contact your financial institution/bank directly to dispute it, and they may process a refund, as this would be considered a fraudulent charge.
You may also need to have your card blocked and request a new one.
Thank you for your understanding! Please let me know if you need anything else.
Best regards,
Darhyl