how do I restore deleted contacts

Contacts are neither stored locally on an iPhone nor in SIM. They are synced to an email account that you had Google, iCloud, AOL, Exchange, Outlook, Yahoo or any Other

If Contacts on iCloud, try this --> Restore contacts, calendars, bookmarks and more using ...

1. How many Contacts account (email client server) you have?
2. What is your default Contacts Account?
3. Which email account you are using to store Contacts?

• See the GIF below for Contacts and Default Account

• Learn how to add an email account and make it default (Watch the GIF)
• This example is for Gmail but the process remains same for all Google, iCloud, AOL, Exchange, Outlook, Yahoo or any Other

If you haven't backed up the changes (deleted contacts) and you do have a most recent backup onto iCloud, and you're confident of such a thing, and you believe that backup had all the contacts. Then I will suggest you erase the phone and restore from recent backup.