101 question - empty extension - basics

I’m running asterisk on a Debian machine. Currently I have 2 Ipphones and a PC with a SoftPhone connected to it. Through, web based interfaces from the phones and the IPBRICK software, I gave them extensions (122,123 and 125).
They all communicate and can call each other quite well.
This is what confuses me, since I’ve emptyed the extensions.conf file, to test what would happen with the calls.

I also tried this simple plan

exten => 122,1,Answer()
exten => 122,2,Playback(pbx-invalid)
exten => 122,3,Hangup()

in the said file, but it has no effect. Why is this? and why do the calls continue even without any related code on the extensions.conf file?

Best Regards!!

P.s. - the extension code is very simple just for test purpouses…
the ide, was when someone dialed 122 (because of the ipphones configs, i changed it to 130), or 130 in the test, the caller would hear a sound, and the call would hang up