GetLicenseNamesByGUID.ps1

# Get Office 365 License Names from GUID

function Get-LicenseNamesByGUID {

    param( [string] $GUID )

    [Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12
    $wc = New-Object System.Net.WebClient
    $wc.Encoding = [System.Text.Encoding]::UTF8
    $src = $wc.downloadstring('https://docs.microsoft.com/en-us/azure/active-directory/enterprise-users/licensing-service-plan-reference')

    if ( $src -match "<tr>\n<td>(.*?)</td>\n<td>(.*?)</td>\n<td>$GUID</td>") {

        return [pscustomobject]@{ 
            ProductName = $matches[1]
            StringID    = $matches[2]
        }        
    }    
}

# Example for OFFICE 365 E1 (STANDARDPACK)
Get-LicenseNamesByGUID -GUID '18181a46-0d4e-45cd-891e-60aabd171b4e'