... but this dedicated server provider does it in this way to install the image. And it comes incorrectly.
Really. In this case you should think about switching to another provider. If you cannot trust the provider to setup the environment correctly, you may run into serious issues in case of disaster recovery (if it is required at some point in time). If you are paying for this, you should insist to having the job done properly!
It should basically be possible to create an additional VMFS partition (assuming that the underlying storage is supported). However, this won't be easy, and I've never tried it before, as there was simply not reason for me to do this. If something goes badly wrong, you might need to reinstall the host.
André