I have an iPhone 7 and a red bell with the line through it appears when I increase or decrease the volume. I have tried to unmute the iPhone and have not worked out how to do it. help will be most appreciated.

Hello AWROBINSON888,

Thanks for that info and for choosing the Apple Support Communities. If we understand correctly, you are unable to adjust volume on your iPhone, as you see an icon on the display related to volume. To help with this, please follow the relevant steps in these Apple resources, like if the silent switch is working correctly, and then contact Apple directly if you need any further assistance.

How to put your iPhone on vibrate, ring, or silent mode

If a button or switch isn't working on your iPhone or iPad

Get Support 

Cheers!