powershell script to change Office 365 License from Educ A3 to A1 with CSV

There are many samples available online, my fav one is here: https://blogs.technet.microsoft.com/cloudpfe/2014/01/30/how-to-change-office-365-licenses-in-bulk-respecting-the-license-options/

You will have to modify the $users part to accept the values from the CSV file.