Contact names missing after iPhone update

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

Use iCloud.com to restore and recover iCloud information

Contacts: Restore contacts stored in iCloud on iCloud.com

Unlike some Android devices, contacts are neither stored locally on an iPhone nor in SIM. They are synced to an email account that you have 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.

1. Is this your corporate/organization/enterprise/School Management iPhone? Then please contact the system administrator of your corporate//organisation/enterprise/School Management
2. If it is your device, in that case, do you have any profile installed by your corporate/organization/enterprise/School Management?
   1. Erase the profile added by you If you have installed a profile on your own --> Install or remove configuration profiles on iPhone - Apple ...
   2. Please contact the system administrator of the organization who provided the profile to you