Please, i have been deducted 10 consecutive months 5.88£, without a reason. How can i cancel it and ask for a refund

Can you go to your account https://account.live.com Sign in and go to Services & Subscription, do you see anything that matches the charges? If not, click on Order history instead and anything?

Micosoft lists some other scenarios you can explore: https://support.microsoft.com/en-us/account-billing/how-to-investigate-a-billing-charge-from-microsoft-398c5328-364c-d5e4-ea8f-f5ad60562a93

If you find the charges on YOUR account but you don't recognize making those purchase, for your privacy and security, billing matter cannot be discussed here, nor does anyone helping here have access to such data. You will need to contact support to get it handled. On your computer, launch the Get Help app from the start menu, then type in "Billing" as the keyword. On the next page, you can click on "Contact support" button. Then fill out a few more details and you will be directed to the page where you will have the option to chat with a live support agent.

If you cannot locate the charges on your Microsoft account at all, it's possible that your credit card has been compromised. This means unauthorized charges may have been made on someone else's Microsoft account using your credit card. In such a scenario, you should contact your credit card company to open a dispute case. Microsoft is unable to directly investigate issues related to someone else's account if you contact their Billing Support directly. However, once a dispute case is initiated by your credit card company, Microsoft can then respond specifically to those claims through the dispute process with the credit card company. This is the appropriate channel to resolve such issues, as it ensures proper verification and handling of the unauthorized charges.