Show my caller id, call waiting and call forwarding not loading

Call Forwarding, Call Waiting, Call Merge, Conference Call, Hotspot, VoiceMail (Visual or Normal) all are Carrier Specific features. Contact your Carrier (Cellular Service Provider), the agency that issued the SIM / eSIM to you.

Depending on your network provider those features may not open in iOS

All of them however can be changed by your network provider either by calling them, or using their app, or in most countries by using short dial-in codes.

For example call forwarding dial-in codes.

https://en.m.wikipedia.org/wiki/Call_forwarding

If unanswered (**61)

dial-in this code

 **61*vvv*11*XX#

where vvv is voicemail number

XX is the seconds of ring time up to 29 max

For voice calls: In many countries this is enabled by your carrier only if you are a VIP.

Contact your carrier.

1. Is this your corporate iPhone? Then please contact the system administrator of your corporate
2. 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

I'v had iPhones in UK for about 4 years now with four different carriers and none of that stuff in iOS ever works whereas **61 does

Maybe it works with the main USA carriers.

if that works for your carrier, yes