/etc/sysconfig/network-scripts/ifcfg-ppp0 :

DEVICE=ppp0
NAME=CDMA
MODEMPORT=/dev/ttyUSB0
LINESPEED=115200
PAPNAME=it
USERCTL=true
ONBOOT=yes
PERSIST=yes
DEFROUTE=yes
PEERDNS=yes
DEMAND=no
IDLETIMEOUT=600

/etc/ppp/pap-secrets :

it      *       it

/etc/sysconfig/network-scripts/chat-ppp0 :

''  ATZ
OK  ATDT#777
CONNECT \\c