Extensions between calls blocking

hey

I’m having some problems getting this configure in Box this is my first time attempting to edit any files in asterisk DIR
Question 1
-the file that i need to edit is extensions_custom.conf ?

What im attempting con accomplish

I have 9 range of extinctions that i need to block My range are 20xx , 30xx, 40xx 50xx 60xx 70xx 80xx 90xx
I dont want this ranges to communicate internally.

Base on the information i have been reading this is what i have don but is not working for me

[from-group-20xx]
exten => _[13456789]XXX,1,playback(ss-noservice)
exten => _[13456789]XXX,n,Hangup()
include => from-internal

[from-group-30xx]
exten => _[12456789]XXX,1,playback(ss-noservice)
exten => _[12456789]XXX,n,Hangup()
include => from-internal

Any Help Please