How can I fix iPhone 11 connectivity issues after iOS 18.5 update?

Frankip45 wrote: "...Battery health is at 81%..."

frankip5 ~ 81% is not healthy, being close to Apple's recommended level of 80% for having the battery replaced. So have the weak, aging battery replaced and all will probably be well:

iPhone Battery Service

About genuine iPhone batteries

Repair Provider Verification

(Articles found by searching Apple's Knowledge Base.)

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frankip5 ~ Your iPhone 11 could be 5½ years old and the long process of applying an iOS update to an iPhone with a weak, aging battery can be the proverbial "straw that broke the camel's back." So...

Does your iPhone 11 still have its original battery?

And what's the Maximum Capacity % here?...

Settings > Battery > Battery Health & Charging

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I am finding Apple support a bit dodger sub par re my iPhone 11.

they told me to upgrade the software which I did that’s made things worse

the battery drain, over heating when not being used, the charging % going backwards when I’m on charge- not good

ibe did a factory reset following apples advice no good.

they haven’t followed up with me repeatedly- absolutely appalling support levels

You are not communicating with Apple in this user to user forum, and, while it may be hard to believe, this is a problem specifically with YOUR PHONE, and not hundreds of millions of other iPhones.

Have you tried basic troubleshooting?

Do you have a 3rd party VPN installed, even if you are not using it? If so, delete the VPN profile in Settings/General/VPN & Device Management/VPN. Don't just turn it off; delete the profile. If that fixes it, you can try reinstalling VPN. 

Reset network settings?

• Open Settings
  • Tap General
  • Tap Transfer or Reset Phone
  • Tap  Reset
  • Tap Reset Network Settings

• • This will erase all Wi-Fi passwords, but will not result in any other data loss.

Carts2204 wrote: "...they told me to upgrade the software which I did that’s made things worse

the battery drain, over heating when not being used, the charging % going backwards when I’m on charge..."

Carts2204 ~ Your iPhone 11 could be >5½ years old and the long process of applying an iOS update to an iPhone with a weak, aging battery can be the proverbial "straw that broke the camel's back." So...

Does your iPhone 11 still have its original battery?

And what's the Maximum Capacity % here?...

Settings > Battery > Battery Health & Charging

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Did all that, the iPhone only had issue since iOS 18 onwards. The phone never had any issue prior to all these bloody updates. Had to update otherwise some apps cannot use.

[Edited by Moderator]