1
This forum is just a user to user forum, no-one here has any account access, using any Microsoft account you may have, try using the steps they provide on this link to find out what the payments are for.
Then use the steps they provide on this link to cancel whatever that payment was for and get a refund.
2
With regards to the cheapest Microsoft 365 plan, what Office apps do you use, there are various options, including subscription based versions of Office and also one-time payment versions of Office.