Using the New-ADUser cmdlet -Name parameter not working with a variable input

Hi, please help me with my script below. I have set a couple of variables $Fname and $Lname and are using them to fill out most of the New-ADUser cmdlet parameters for a new user account. However, it seems New-ADUser -Name $Fname $Lname doesn't work because it thinks $Lname is an argument instead of part of the string input, any ideas?

Below is the code and the error,
Thanks

function New-CompanyUser {

    param (
        [string]$Fname = (Read-Host 'Enter new user First Name only'),
        [string]$Lname = (Read-Host 'Enter new user Last Name only'),
        [string]$Description = 'New User Account',
        [string]$Password = (Read-Host 'Enter a valid password for new user account')
    )

    Begin {
        # Get OU Users
        $OUU = "OU=Users,OU=FolderIT,OU=Folder,DC=Domain,DC=Domain"
        $OUU

    }            
    Process {
        $check = Get-ADUser -Filter {Name -like $Name} -SearchBase $OUU
        
        $check
        
            if ($check) {
                write-host "The user name $Name already exist"; break
            }
            else {
                write-host "Creating a new user account $Name"
            }

        # Add new user to OU Users
        $newUser = New-ADUser -Name $Fname $Lname -GivenName $Fname -Surname $Lname -Description $Description -DisplayName $Fname $Lnam -Enabled $true -SamAccountName ($Fname + '.' + $Lname) -AccountPassword (ConvertTo-SecureString $Password -AsPlainText -Force) -ChangePasswordAtLogon $false -Path $OUU -PassThru
      }
      End{}
}

              

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New-ADUser : A positional parameter cannot be found that accepts argument 'Last'.
At line:31 char:20
+         $newUser = New-ADUser -Name $Fname $Lname -GivenName $Fname -Surname $Ln ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidArgument: (:) [New-ADUser], ParameterBindingException
    + FullyQualifiedErrorId : PositionalParameterNotFound,Microsoft.ActiveDirectory.Management.Commands.NewADUser