Hi @MOUTT
Thank you for posting in the community.
The plan is usually based on how many active profiles you have available in your account and therefore shows the paid plan equivalent to having 20.000 active profiles coming directly from your integration or mirgration to the platform.
You can read more about billing here:https://help.klaviyo.com/hc/en-us/articles/115000976672
If you have a large amount of active profiles that are currently not subscribed I would recommend to supress these either through a webhook or manually. You can read more about that in this article: https://help.klaviyo.com/hc/en-us/articles/24263920096027
Hope this helps - and have a nice day!