Uneditable Contact Causing Missed Calls on iPhone

1. If it is your personal device, in that case, do you have any profile installed by your corporate/organisation/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. Or please contact the system administrator of the organisation who provided the profile to you
2. If you want to turn on SSL trust for that certificate, go to Settings > General > About > Certificate Trust Settings. Under "Enable full trust for root certificates," turn on trust for the certificate. Apple recommends deploying certificates via Apple Configurator or Mobile Device Management (MDM). --> Trust manually installed certificate profiles in iOS and iPadOS ...

• Is this your corporate iPhone? Then please contact the system administrator of your corporate
• If it is your personal device, in that case, do you have any profile installed by your corporate/organisation/enterprise/School Management? Then also, please contact the system administrator of your corporate/organisation/enterprise/School Management.
• Else, delete and add the mail account which hosts your contacts in the IOS mail app. It is a matter of 1-2 minutes only.

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

• See the GIF below for Contacts and Default Account