Um, unfortunately you've got the worst one: A hyperban! Dx
Changing the Local Friend Code SEED won't make a difference with this type of ban. You're unable to access any Nintendo Network services AT ALL (which results in error code 022-2812). The ban is tied to the deviceID, which is hardcoded into the 3DS System on a Chip (SoC). You can only evade this ban by spoofing the DeviceID, which can only be done in a custom build of Luma3DS. Even so, you've lost your Nintendo eShop purchase history anyway, which I know, really sucks. And I'm really sorry to hear that it's happened to you. :c
You can however, unlink your NNID from your 3DS console though by changing the nnidsave.bin, or do a system format. That should be able to restore your eShop access, but you won't be able to use Nintendo Network services without spoofing your DeviceID. Also, the DeviceID has to be from an actual 3DS console, it cannot be made up, otherwise the servers will detect it as invalid.