Trying to check if users are part of a group and if not add them

I am writing a bash script to add users but I am stuck when adding users to groups.

What I have:

#--------------------------------------------------
#This First reads the users.csv file splits up the data
#Checks if the users exists and if not  makes them and gives them a password. 
#it will then 

file="users.csv.1"
Count=0


while IFS=";"; read email birthDate group sharedFolder
do
    echo -e "Email: $email"
    firstCharacter=${email:0:1}
    echo $firstCharacter
    local_part="${email%%@*}"
    last_Name="${local_part##*.}"
    echo "$last_Name" 
    UserName="$firstCharacter$last_Name"
    USERID="$UserName"
    egrep -i "^${USERID}:" /etc/passwd
    if [[ $? -eq 0 ]]; then
        echo "User $USERID exists in etc/passwd"
    else
        echo "User $USERID does not exists in etc/passwd"
        
        
    fi
 
    sudo useradd $UserName
    echo -e "UserName: $UserName"
    echo -e "Password: $birthDate" | tr -d '/'
    echo "$UserName:$birthDate" | sudo chpasswd
    echo -e "Birth Date: $birthDate"
    
    if [[ "$group" == "staff" ]]; then
        usermod -a -G "$UserName" staff
    elif [[ "$group" == "visitor" ]]; then
        usermod -a -G "$UserName" visitor
    elif [[ "$group" == "sudo" ]]; then
        usermod -a -G "$UserName" sudo
    else
        echo -e "no group to add to" 
    
    fi
        
    
    echo -e "Group: $group"
    echo -e "shared Folder: $sharedFolder\n"
    
    
     
done < "$file"

My problem is that it will keep coming back and saying usermod: user 'staff' does not exist

I do make the groups at the start of the script. Shown here:

if [ $(getent group staff) ]; then
echo "group staff exists."
echo $'\n'
else
echo "group staff does NOT exsit."
echo "one will be created now"
sudo groupadd staff
echo "staff group has been created" 
echo $'\n'

fi


if [ $(getent group visitor) ]; then
echo "group visitor exist."
echo $'\n'
else
echo "group visitor does Not exist."
echo "One will be created now" 
sudo groupadd visitor
echo "visitor group has been created" 
echo $'\n'
fi

I am not sure what I am doing wrong because I get the checks back at the start of the scripts saying that the groups exist.