Microsoft has expanded their self-service offering from Power Platform licenses to also allow users to purchase Viso and Project licenses themselves. This can become very messy for companies trying to track their Office 365 expenditure and licensing. Fortunately it can be disabled using the following PowerShell

# Install the PowerShell module using the command
install-module MsCommerce

# Connect to Commerce endpoint. Log in with GA
Connect-MsCommerce

# List policy allow self-service purchase
Get-MSCommercePolicy -PolicyId AllowSelfServicePurchase | fl

# List current plans allowing  self-service purchase  
Get-MSCommerceProductPolicies -PolicyId AllowSelfServicePurchase

# Set policy to disabled for any that are enabled
Get-MSCommerceProductPolicies -PolicyId AllowSelfServicePurchase | ? {$_.PolicyValue -eq "Enabled" } | ForEach {Update-MSCommerceProductPolicy -PolicyId AllowSelfServicePurchase -ProductId $_.ProductId -Enabled $False }

More info is available in Tony Redmond's excellent article on Petri - https://petri.com/microsoft-expands-self-service-license-purchasing-to-visio-project?_hsmi=93447999&_hsenc=p2ANqtz--CT8FawwP2Rf-DbrazPLt6KLQrT5y_93cPp_-o0gdLTLfImIjdqU5D58iFbXdpeR4wJWB3Mx4uOkagz_NLM3sRz0eD71bKXOY18xR2ESKHcooDUa0