Why am I getting ‘Get-MgUser’ not recognized error in PowerShell?

I'm having an issue where I keep getting the error message stating that 'Get-MgUser' is not recognized as a cmdlet, function, script file, or operable program. I'm also seeing a similar message when trying to use Update-MgUser. I've already installed the Microsoft Graph PowerShell module and am using the following script to connect and update user phone numbers:

```powershell
# Connect to Microsoft Graph
Connect-MgGraph -Scope User.ReadWrite.All

# Read the CSV file
$users = Import-Csv -Path "C:Tempnumbers2.csv"

# Loop through each user in the CSV to update the PhoneNumber
foreach ($user in $users) {
$userPrincipalName = $user.UserPrincipalName
$PhoneNumber = $user.PhoneNumber

if ([string]::IsNullOrEmpty($PhoneNumber)) {
Write-Host "PhoneNumber is empty for user '$userPrincipalName'. Skipping update." -ForegroundColor Yellow
continue
}

$existingUser = Get-MgUser -UserId $userPrincipalName -ErrorAction SilentlyContinue

if ($existingUser) {
if ($existingUser.PhoneNumber -eq $PhoneNumber) {
Write-Host "User '$userPrincipalName' already has PhoneNumber '$PhoneNumber'." -ForegroundColor Cyan
} else {
Update-MgUser -UserId $userPrincipalName -PhoneNumber $PhoneNumber
Write-Host "User '$userPrincipalName' updated PhoneNumber to '$PhoneNumber' successfully." -ForegroundColor Green
}
} else {
Write-Host "User '$userPrincipalName' not found. PhoneNumber field is empty." -ForegroundColor Yellow
}
}
```