To enable call-back, go to the account editing window,
then go to the PPP tab, check the
"Provider will call-back (CBCP)" checkbox
and enter your phone number in the
"Call-back Phone Number" field.
If you use command line interface,
then use account attributes
callback
and callback_phone_number
.
If the program fails to establish a connection and you see message
/usr/sbin/pppd: unrecognized option 'callback'
then recompile the ppp package with CBCP support, see Compiling ppp with CBCP Support.