checking if a user exist +script does not work

Hello everyone

I am trying to create a script that checks whether a user exists or not in AD. I have seen other posts with similar problems but I can not make mine work. :(

Here is my script which to be honest is made up of bits and pieces from the web:

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Import-module activedirectory
$objOU=[ADSI]"LDAP://OU=dummyOU,DC=testad,DC=bk,DC=co,DC=uk"
$source=import-csv ".\Book1.csv"

foreach ($data in $source)
 {
   #store values from $source to variables
   $cn=$data.cn
   $firstName=$data.firstName
   $lastName=$data.lastName
   $userPrincipalName=$data.UserPrincipalName + "@testad.bk.co.uk"
   $sAMAccountName=$data.samAccountName
   $password=$data.password
   $fullname=$firstname + " " +$lastname
   
  #Write-Host $fullname
  $pattern="$fullname"

  #write-host $pattern

  foreach ($username in $pattern)
             {
              $username = get-aduser -filter {name -eq $pattern}
         
      if ($username -eq $pattern) {"User $fullname does not exist"}
         else {"User $fullname exists"}
             }
}

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My CSV file looks ike this:

CN_FirstName_Lastname_UserPrincipalName_SamAccountName_password

Bill Brown_Bill_Brown_ubgg01_ubgg01_password

Bill Green_Bill_Green_ubgg02_ubgg02_password

Regardless of the fact that the user exists or not when I run the script I always get:

User Bill Brown found in AD

User Bill Green found in AD

Obviously there is something wrong but I don't understand what that is. This is my logic which in somewhere in practise it goes wrong.

1. Import data from csv file.
2. For each line in the csv file map the values to variables so that later can be used to create an non existing account
3. store the $fullname of the user in a variable called ($pattern)
4. then for each line in variable $pattern look if the $fullname appears in AD using get-aduser (I believe that's where I am wrong, i'm not sure whether you can use a foreach loop in this case.)
   
5. if user exists print: user exists, otherwise print: user does not exist

Please help if you can. Thank you