How do you prevent your phone from locking during voice calls? Mute/unmute features? Are there any? Please help?

Question

Here is the problem - I am often on conference calls.  My company, for security reasons requires that I use the lock phone feature.  However, I will be on a call, I have muted myself, then the phone locks.  I then have to key in my password, and unmute my phone.  This prevents me from "jumping in" the conversation appropriately.  I either sound like I'm not paying attention or worse, I'm talking over someone else and seem rude.  I have tried to search for any of the following features on the iphone 5 c.
Prevent phone from locking during phone calls
Set a button on the phone as mute/unmute
Find a headset that has a mute/unmute feature
I am not the only one at my company struggling with this so I'm thinking others might be too and that there is a solution!
Please help!
Thank you.

Answer 1

Sounds like you need to upgrade to the iPhone 5s
The 5s has Touch ID
You can unlock your phone with your finger instead of typing in a key code
No swiping to unlock either, just touch the home button
You can enrol multiple fingers as well
Here is a video of it in action
http://www.apple.com/iphone-5s/videos/#video-touch
Or wait and see what iPhone 6 has to offer
That being said, as desiel vdub posted if the phone is up to your face, the proximity sensor should turn the screen off
And when you lower the phone turn it back on again
Not sure about the phone locking when your on a call doesn't sound right