Un update just to know.
I have found the solution adding this code:
[sub-pincheck]
exten => s,1,Set(CALLERID(num)=${ARG3}${CALLERID(num)})
exten => s,n,Return()
; end of [sub-pincheck]
in file /etc/asterisk/extensions_override_issabel.conf
Then a prefix can be added in "Route Password" section of the Outbound Route.
In this case we dont need a route password, solution is not perfect at all, but it works perfectly.