iPhone Calls icon has a red number on it that will not go away

I have an iPhone 13 Pro Max running iOS version 26.2.1

After the last iOS version, this problem has appeared but the user interface to make calls changed dramatically

and I don't understand why- it is confusing and unintelligible.

What I notice is that if I click on the phone icon (e.g. a key usage), at the bottom there are symbols called "Calls" - with a clock, "Contacts" with a person, "Keypad" with a collection of dots and a magnifier. A red number appears on the "Calls" icon. On the Calls screen, there is an edit button at the top left and on the top right are filters. At the very top are icons of people who have called or been called (I don't really know) and at the bottom are "Recents" - a list of names or numbers of calls. Again, I don't really know if these are missed calls, but when I filter for "Missed calls" I see red text.

The problem I have is that the Calls icon has a red number on it. I couldn't tell which call it was alerting me to or why. I tried randomly calling back and then hanging up a few numbers but this is dangerous and impractical. I also tried turning off the phone by holding a bunch of buttons that a user advised Ankurbaba1963 to use - really confusing-hold one button then another, then all three? I also had Siri turn off the phone. What happened is that the red number went away briefly and then reappeared.

I solved my own problem while doing this. I used the filter at the top right to find missed calls, then voicemails. In the voicemails there was one that I had never listened to. I listened to it and the red number finally seems to have gone away. The voicemail option in iPhones is truly irritating because it won't clear unless you listen to an entire voicemail and often - especially with junk calls- I don't need to listen to the whole call in order to understand what is being said. But, in this case, I waited through the response and it did clear the number.