Generally, see https://support.microsoft.com/en-us/account-billing/how-to-investigate-a-billing-charge-from-microsoft-398c5328-364c-d5e4-ea8f-f5ad60562a93 .
Note that if you signed up for a trial subscription, and then forgot to cancel, the trial will be converted to a paid subscription. If that is what happened, your account should let you cancel the subscription. You can go to https://account.microsoft.com/services and test with your various @outlook.com and @hotmail.com accounts, and with a bit of luck you will find the correct one. See also https://support.microsoft.com/en-us/office/cancel-a-microsoft-365-subscription-46e2634c-c64b-4c65-94b9-2cc9c960e91b .