How do I get rid of the latest iPhone update?

While I do agree with SravanKrA that more detail in your post would let us possible address any specific issues you may be having, I do not agree with SravanKrA's verbose summary of the situation. I have done multiple upgrades on many different types of Apple devices over several decades. Some included some good features, but they also included changes that frankly made the interface harder to use or removed things that were really good but for some inexplicable reason Apple decided to remove. With some changes it is a matter of adapting to a different way of doing things. As for the things Apple removes, you can sometimes find alternatives (this is a lot easier on computers) or workarounds.

In the end though, you cannot now downgrade any iPhone or iPad changes you have made. In the future I would advise that prior to making any major system upgrades (security updates should not produce any real noticeable changes) that you browse the web, and in particular this forum, for discussions regarding what others are experiencing. Not everything is "rumors" and yes, some things can be the OS' fault. As far as the iOS update, you have the freedom to assess what steps you wish to take. Security features are perhaps the most important things to consider. As for other features, you can decide if you need them. I mostly use a computer and I know that after reviewing what the most recent macOS offered didn't really have anything that interested me and I decided to simply skip it.

I offer that to you as a different perspective on updating.

Unfortunately you cannot downgrade iOS.

It's not always the iOS update's fault!  Many things can cause phone problems.  If you tell people you think it's an iOS update, it might make it harder to fix or find a solution for the real issue.

Remember, the right question often leads to the solution!

Was/Is your device Jailbroken? If that's the situation, please be informed that attributing the issues to iOS updates may not be accurate.

iOS updates aim to enhance user experience, boost security, and fix bugs rather than disrupt core features. The majority of the issues after updates might stem from underlying, unmentioned factors. Updates won't typically alter personal data but may refine settings or features. Backup before major updates for safety. Review Apple's update details and backup advice for a smooth process.

Kindly consider checking your settings and addressing any device issues before attributing the issue to external factors. This could be a pure coincidence that the iOS update affected the iPhone functions.

Before initiating a standard iOS update, it's advisable to create a backup. Have you completed this step? If yes, proceed with the restoration from the backup.

See what each update does: OS — iOS 26, About iOS 18 Updates, About iOS 17 Updates, About iOS 16 Updates, About iOS 15 Updates, About iOS 14 Updates, About iOS 13 Updates, About iOS 12 Updates, and so on...

Was your device Jailbroken? If that's the situation, please be informed that attributing the issues to iOS updates may not be accurate.

I have been updating my devices ever since I bought my first device in 2009. iPhone 3Gs, 4S, 5, 6, SE (1st Gen), 7, 8 and iPhone 12 Pro, iPad Pro, iPhone 13, Macbook Air 2019, MacBook Pro 16"

I never had any issues with any iOS, iPadOS, or macOS updates to date.

I would personally recommend everyone update their devices instead of listening to rumors from people who may not have kept their devices free from any spurious software.

iOS / iPadOS devices cannot be hacked or infected with Virus / Malware / Spyware if it is updated to the latest iOS/iPadOS unless you have intentionally downloaded spurious software or unauthorized apps directly from the internet and installed them on your device or/and have Jailbroken. 

iOS updates generally aim to enhance user experience, boost security, and fix bugs rather than disrupt core features. Issues after updates might stem from underlying, unmentioned factors. Updates won't typically alter personal data but may refine settings or features. Backup before major updates for safety. Review Apple's update details and backup advice for a smooth process.

This seems purely coincidental, so please check the settings on your device.

See what each update does: OS — iOS 26, About iOS 18 Updates, About iOS 17 Updates, About iOS 16 Updates, About iOS 15 Updates, About iOS 14 Updates, About iOS 13 Updates, About iOS 12 Updates, and so on...