You need to go through the upgrade process before the 29th to take advantage of the free upgrade, unless MS changes it .
The easy way to get the entitlement license to use later, swap a blank hard drive into your system and run the windows 10 install from a USB key. Use your windows 7\8 key...
Use the media creation tool again and recreate the USB install drive. Pay attention during the creation and select the options to update a different pc and be sure that you are using the right version of the software for the version you have a key for.
Then reinstall with the new usb drive.
So you bought an OEM version and then had issues with the license that you bought and agreed too. Sounds about right.....
$200 for an OEM key is about twice the price it should be, $200 is retail version price.
What happens?
I would expect them to turn off access and send the account to collections. OP stated he did go over, pay what you owe for your usage and move on.
But that is correct. I have met the man\woman on the streets, they are morons. Content with "entertainment" in the likes of the kardasian and their swirling BS.