I have a simple pbx with two phones, one isdn, another one is a sip phone(granstream gxp2170), the isdn phone respect the italian tone, the sip phone use the american tone.
I think I had configured right my environment
language = it
country=it ; default location
exten => 1001,1,Set(LANGUAGE()=it) exten => 1001,1,Dial(SIP/telefono1,20,Ttm) same => n,Hangup
After restarting asterisk the sip phone still use american tones