How do I restore deleted phone numbers

Go to  https://www.icloud.com/  and sign in.

(You can do this on mobile/browser, safari, a different device, desktop computer; etc.) Whatever makes it easiest for you….

Tap on Account Settings , scroll all the way down and tap on Restore Contacts…..

This will allow you to use an iCloud backup , and you should be able to see or even copy the contacts from it that you had before….

****Note that if your iCloud is full, then you won't be able to back up….therefore, you will most likely see no back ups to restore…

Keep in mind that iCloud backups are done automatically; Any Previous backups normally shouldn’t be deleted either, unless you have done it manually.

What is your default Contacts account? If none, please add an email account and enable contacts.

See the pic below

Unlike some Android devices, 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 you have a corporate email account added through a profile on your device, please check with your organization's system administrator.