Call2Teams - Customers
As an end Customer you cannot amend your own licences via the Call2Teams portal.
You will need to contact your supplier to request these as they are added at the Account Management level.
You can see how many licences you have available and whether any of your users are unlicenced, from the Users tab in your portal. Failing that, you would need to refer to your supplier.
Microsoft Direct Customers
A licence increase/decrease should be effective immediately