Check your phone’s Trash/Recently Deleted folder in the Contacts app
Restore contacts from your Google account contacts trash
Restore contacts from your iCloud contacts recovery
Restore from a recent phone backup
Restore from a computer backup such as iTunes or Finder
Check whether contacts are synced from another account like Gmail, Outlook, or Exchange
Sign in to the same account used before the contacts were deleted
Export contacts from another device that still has them
Ask the contact owner to resend their details
Use a data recovery tool if no backup is available
Contact your carrier or device support if the contacts were stored through their service