Okay so unfortunately Apple took the “Mute/Unmute” option away from assistive touch menu. I’m finding this out the hard way when I upgraded to the 16pro max. The only way to mute and unmute is:
Control center: swiping down from the top of your phone and clicking the bell icon
Action button: Setting mute/unmute through the action button (I don’t recommend because I prefer flashlight)
Shorcuts App: You can set a command in the Shorcuts app that you can add to the Assistive Touch menu that’ll let you Mute/Unmute your phone.
Personally, I believe all these options to be tedious and not the best FOR ME because the assistive touch menu had it all in one place. The newer model iPhones will NOT have the assistive touch mute/unmute option anymore because they want us to use the action button instead. Unfortunately.