How to delete a record from a file using bash scipt?

I am very new to scripting (one week in) and was trying a program that creates an address book for the user where they can save the details of their friends. First I ask the user to name their address book and I store it in the variable 'abname', then I take the necessary input from the user and print it in the text file abname.txt

My Problem: How can I delete a record corresponding to the id the user has provided? Here is what I did:

#!/bin/bash


id="1"
while(true)
do
    echo -e "\nMenu\n1.Create new Address Book\n2.View all contents of address book\n3.Insert new record\n4.Delete a record\n5.Modify a record\n6.Exit"
    echo -e "\nEnter your choice: "
    read ch
    echo -e "\nYou have selected choice: $ch"
    case $ch in
    1)
    echo -e "\nEnter the name of the address book"
    read $abname;;  

    2)
    echo -e "\nAddress Book: $abname" #the name of the address book doesn't print here for some reason
    echo -e "\nID\t Name\t Age\t Address"
    cat $abname.txt;; #prints all content of the file

    3)
    echo -e "\nId Of Person is: $id"    
    echo -e "\nEnter Name of Person: "
    read name
    echo -e "\nEnter age: "
    read age
    echo -e "\nEnter Address: "
    read addr
    printf "$id\t $name\t $age\t $addr\n" >> $abname.txt
    id=$((id+1));; 

    4)
    echo -e "\nEnter ID of Person who's record is to be deleted: "
    read id
    grep -v "$id" $abname.txt > $abname.txt
    echo "Record is deleted"
    cat abname.txt;;

    5)
    echo -e "\n Todo";;

    6)exit;;
    *) echo -e"\nInvalid choice";;
    esac
done

Additional Help: If the file abname.txt already exists, I want to update my local 'id' variable corresponding to the last person's id in the text file, I tried doing this but it didnt work, what am I missing here?

if [ -e $abname.txt ]
then
    source <$abname.txt>
    id = $id
fi