Someone else had asked about double billing on an annual subscription, but the topic has been closed as a support matter.
However, this seems like this is a bug with how annual subscriptions that span calendar years are handled. Specifically, the subscription for the other post started in November 2020, and ours started in August 2020. Both accounts started being charged monthly in January.
Did you reach out to the Figma support team?
Yes.
Hi, I’m having same problem with you. Already paid for annual subscription but still charged for monthly. And now all of my files get locked. Still waiting response from figma support.
RFNco, Is your problem solved?
Hi! I have the same problem 
and I’m concerned that the file editing option will be locked before someone reaches out to me. This is what was written in the automatic email response “We are experiencing a high volume of requests and our current response times are slower than we’d like.”
Since it’s not a one time bug, I’m genuinely wondering why do they not work on solving this problem? It’s extremely upsetting to have to deal with this, as a paying customer.
because it makes money 
Don’t worry though, recently the support has been answering within a day or two. And you can most of the time get a refund if something goes wrong.
Patience is not my strong point 
I should have waited more before writing this comment, but all the other comments on this forum made me concerned that support is not very quick to answer.
They actually answered within an hour and were really helpful. Turns out, it was actually my fault.
For anyone having the same issue: make sure that the total number of editor seats on your team matches the # of editor seats you paid for in your annual subscription. This one can be tricky for new users such as me, hence the whole “issue” So no bug here 
