There are situations where you want to block users from signing up for trial of office 365 services like streams,Flow,Power BI etc.
We have been given this task as it was interfering with our project where we were turning ON office 365 services in a planned manner.
You will not be able to restrict all services but most of these will abide the settings.
Log on to MSOL thru powershell: (Refer how to connect to MSOL : https://techwizard.cloud/2015/04/30/connecting-office-365-via-powershell/)
Type below command to check current settings:
Get-MsolCompanyInformation | fl AllowAdHocSubscriptions
If value comes out to be true than it means that users are able to sign up for services trials.
Turn the value to False to disable sign ups.
Set-MsolCompanySettings -AllowAdHocSubscriptions:$false
After this has been done We have tested the services and trials were successfully blocked.
Note: Some services don’t have signups available and some don’t even require a license.
Irrespective of above settings,we want to test all (These can change as Microsoft make changes so please test yourself, below are our test results for reference)
Delve – Working without license
Forms – Not working (signup blocked after Settings was set to False)
TO-DO – Not working
Stream – Not working (signup blocked after Settings was set to False)
Staffhub – Working without license (Settings can be updated to apply license Check)
Flow – signup blocked after Settings was set to False (require license)
Powerapps – signup blocked after Settings was set to False(require license)
Microsoft Teams – Not working without License
Planner – Working without license
SWAY – Not working without License
PowerBI – Not working without License (signup blocked after Settings was set to False)
Yammer – Working without license (Settings can be updated to apply license Check)
EOL – Requires License
SKOB – Requires License
Office ProPlus – Requires License
For services, Where signups were available earlier, are now blocked.
Users get below message when they try to SIGN UP.
Tech Wizard
Tech Wizard 
Pingback: Avoid Users from Signing Up for Office 365 Services Trials | Cloud Computers Guide
This command does not look like it is available. I do not see this property.
I just checked its still available, I am assuming you have MSOL module on your machine.
Pingback: Teams: Can you do private chat only? – @Microsoft365Pro
is it true that for users which are created in Office 365 I can not prevent the sign in in Flow with the free license?
You can prevent signups using the above method.
Is it possible to block trials for specific services? I am looking for a way to block only Microsft Teams service trials.
You can run a powershell script & remove the trials from license subscription, apart from that I can not think of another way. if you ant gui way than go to portal.azure.com , under azure ad go to licensing and you will see all the users that have signed up for the teams trial.
If any users is consuming an existing trial, after executing of this command – will his/her trial come to end ? Also, is there a way to fetch report showing details of currently which user is using which trial app in O365 tenant?
no this will apply only to new users
In-case any existing user is using trial O365 license for any of the service, what will be the impact on him/her – will the trial continue or get halted immediately after we disable ad-hoc Subscriptions ?
no this will apply only to new users