Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
Dear Ali Yassine1
Thanks for choosing Microsoft Community.
Based on your description, I know your consult. For this, I need to confirm with you have you tried clear the browser caches and re-sign in with the browser's InPrivate mode and check the result. If this cannot work, please be kindly to change another browser to purchase the Mirosoft365 Basic and check the result?
If you tried all of them, for this, I sincerely suggest you contact our Billing Support phone call team. Here is the way to contact them: Get support - Microsoft 365 admin | Microsoft Learn. The engineers there will provide you further help via phone call.
Your understanding and co-operation are highly appreciated.
Thanks for your precious time, Have a nice day.
Sincerely
Katherine