How to get rid of unneeded operator from Microsoft 365 and operate the administration by yourself?

We are only a three-person organization. 

Currently, our Microsoft 365 contract goes through an external operator, from whom we have to buy new licenses for our own account. This comes way back from history.

The service from the operator is lousy. It took us two weeks to activate the license for our new email address. We want to get rid of the external operator and manage our own account independently.

How can this be done? Can we do this transfer ourselves through our own admin panel?