Yes gates 22 and 23 are often quiet and are relatively large gates in terms of surface area. But mid way in the passageway between First Lounge and CCR may be an alternative - you won't be disturbing anyone there and everyone passing by you is intent on going somewhere else.

If you need a cabana for just a call and for a few minutes, let the staff know since that won't need the cabana to be fully tidied up for use. There is also the area at the end of the toilets' corridor. There are some staff offices beyond though. If the terrace isn't too busy then the far corner by the emergency escape passage can be quiet, so long as you are able to keep your voice down. Most mobile phones work better that way anyway, thanks to accentuating microphones, though some people will never get that concept.