I updated to 16.4.1 (a) and now I can’t call anyone

Apple does not support downgrading the operating system.

Contact your carrier and work with them to help resolve the issue.

Try a forced restart to see if that resolves the issue.

• Press and quickly release the volume up button

• Press and quickly release the volume down button

• Press and hold the side button.

• When the Apple logo appears, release the button.

Force restart iPhone - Apple Support (IN) Force restart iPhone - Apple Support (IN)

Users can back out of the (a) update.

How to Remove Rapid Security Response Updates from iPhone & iPad

1. Open the Settings app
2. Go to “General” and then choose “About”
3. Tap on the version of iOS / iPadOS shown in the About screen
4. Choose “Remove Security Response”

I experienced a similar issue with iPhone11. After upgrading to 16.4.1 (a) I could only get a 3G cellular connection. Thinking that it may have been caused by the update, I uninstalled the Rapid Security Response update, however, the issue persisted. I had another iPhone in the house and switched out the Sim card as a test and successfully connected with LTE. I replaced the Sim card and contacted provider support to update the ICCID on the phone. Issue resolved.

I now have the RSR 16.4.1 (a) pending in Software Update. I will not be updating at this point. My question is, will Apple be fixing this update and notifying customers?

https://www.macrumors.com/how-to/remove-rapid-security-response-updates-ios/

If the option to remove the update is not present then you are not on the 16.4.1(a) update. What version is shown when you tap the About button? Have you updated to 16.4 instead?

Where are you located? Most carriers worldwide have shut down their 3G networks, or will in the next few months. In the US there are NO 3G networks still in use; the last one (Verizon) was shut down December 31. AT&T, T-Mobile and Sprint shut their 3G networks last summer.

If the issues you mentioned are indeed caused by iOS, it's likely that numerous users who have upgraded to iOS 16.4.1 (a) are experiencing similar problems. However, in order for the community on this forum to provide helpful responses, it would be beneficial for you to specify the nature of the issue you are encountering. Without this information, it may be difficult for others to address your concern effectively.

With the limited information that you have provided, It is hard to even guess the problems faced by you. 

You may get faster and better responses to your query by --> Writing an effective Apple Support Commun… - Apple ...

Please re-post with detail so that someone else can help.

Yes, I had this happen. My phone will not read the SIM Card now. All I get is SOS at the top of my screen after I did the update. We even had a new SIM Card put in and they said it still wasn't working. My phone was working perfectly fine prior to this. They told me I had to get a new phone to fix the issue.

No.

I have installed every ios update since the iPhone 3.

I have never had a single issue with any of them, including the recent critical security updates.

The majority of people who update don't have any issues with updates.

Your decision to leave your phone vulnerable to actively exploited security issues is up to you.

The security patches will be rolled into the future point update coming sometime in the future.

Me too. I need the 3G option and it isn’t there. I called my provider and they did a reset and it worked for a few minutes and then stopped again. They said it was the iOS update and it couldn’t be reversed. Apple problem. Help!! I run a business from my phone.

This is not a carrier problem. I talked to them first. This is a problem with the update.

I did this but there is no option to 'Remove Security Response' as per point 4.

This isn’t helpful weeks later when we had to purchase a new phone! I think Apple needs to reimburse some of us who have purchased new phones because of this update!

Whoever told you that you needed to buy a new phone was feeding you disinformation.