exten => 02********,2,Dial(${LORENZO},20)
exten => 02********,3,Dial(${RECEPTION},20)
;here is the new line
exten => 02********,4,Dial(${MOBILENUMBER},20)
Noone can tell you what to put exactly because every configuration and deployment is different. If you provided the full configuration someone might tell you exactly, but otherwise people here can only provide general guidance which has been done.
There’s nothing else anyone can add to try to explain things clearer. Without an understanding of how Asterisk is configured we would need to write your configuration for you.
You should first go through this wiki or http://www.asteriskdocs.org/ (based on old version of Asterisk but very useful to start with) to find answers for most of your questions.
–Satish Barot
I wasn’t expecting that you will copy and paste that, so everything between this → ${ } is a variable, in this case you need to define ${MOBILENUMBER} in your extensions.conf to make it work. Or you just can put your tech/sippeer/number in example DIAL(SIP/mytrunk/123456789) where the technology used is SIP, you have a service provider defined in sip.conf called mytrunk and the number to dial is 123456789.
Read the link that Satish sent you and you will learn a lot.