Why doesn't my mute switch work?
I can't mute my phone with the mute switch. How do I fix this?
Hi. You could try ti replace it.
You can buy the part here: iPhone 4S Headphone Jack & Volume Control Cable
Here is a guide how to fix it/replace it: iPhone 4S Headphone Jack Cable Replacement
You can also turn on "AssistiveTouch"
Tap Settings > General > Accessibility > AssistiveTouch.
More info about AssistiveTouch: Apple support