If you’re wondering how to add iphone dial extension on iPhone contacts then you must follow these steps:-
1. The initial step is to open the Contacts app.
2. Now tap on the contact on which you want to add an extension.
3. Then tap on the Edit button which is located on the upper right corner.
4. Now tap on the number you are adding an extension to.
5. Then tap and hold on the symbol button on the keypad.
6. Now tap on pause to insert a comma after the number.
7. Then enter the extensions and finally tap on Done to save.