Blocking withheld numbers on iPhone 5

If withheld numbers are blocked, what happens if there is an important call from an emergency service e.g. hospital etc. Most use withheld number.

If withheld numbers are blocked, what happens if there is an important call from an emergency service e.g. hospital etc. Most use withheld number.

That's down to the end user, but there are companies you cannot call if you withhold your number also, as they have blocking enabled for 'unknown callers'

I use the should I answer App, or does it not work on Iphones.

Never seen that option on my phone

Never seen that option on my phone

It is an app on the play store that you need to install.