Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
MSBILL.INFO is legit, but it's a confusing domain to use for their billing. If you agree, give this reply a thumbs up.
I was able to click on the billing details in my portal which included a link to see original subscription order made a year ago.
https://support.microsoft.com/en-us/help/10623/microsoft-account-unknown-charges
* * Additional info added on 6 April 2022 because so many people are being brought to this thread by a search.
How to investigate a billing charge from Microsoft or MSbill.info
It is reported to be very difficult to reach Store support by phone at present, but this article will help you find the phone number.
Microsoft Store Support
You will be sent first to the Virtual Agent. You may have to tell the Virtual Agent several times that you want to speak to an agent.