Deactivate Power BI Pro Trial

Dear community

I have found a number of threads on that topic already but none of it seemed to provide a solution.

We have a premium license in our company and we want to go live asap. All users signing in to PowerBI for the first time will go through the self-service Sign Up and end up having a free license, which is enough to consume content in the premium capacity.

However, PowerBI keeps asking users to sign up for the 60 days Pro Trial, via Email, Pop-Ups etc. We want to avoid this at any cost as this is basically destroying our usage concept and is very hard to support (imagine all users asking questions after 60 days when their trial expires).

We want to disable the Pro Trial. I learned that by deactivating the Self Service Sign Up for all users, this can be avoided. This is fine, but in that case, we would need to assign the free license to the entire organization (through a PowerShell script) for which we do not have the time currently. We do not have an AD Security Group containing all Users, hence also the preview function to assign services to AD Security groups is not an option.

Can you help me on that matter to have this solved? is there no setting to have the pro trial pop-ups and email suppressed?

Thank you very much in advance for your help. Hope to get an answer very soon as otherwise, I would need to inform my community that we need to postpone... 

Best regards
Joël