I define oversold for example: 9gb ram sold to customer, even they currently use maybe only 7gb ram and server has only 8gb ram.

My host are never used fully or over what resources they have.

I do not understand what you mean with "cpu-usage is not limited." - "How is that not oversold then?" ? That´s just the same like webhosting. If you do webhosting and there also no cpu-usage-limit, then you do overselling there!?

Maybe you just wait, if a customer complains here about overselling and not getting what he´s paying for. But I think, you might wait a long time.