>/etc/ppp/ppp.conf явно кривой, поэтому просьба показать его
pptp:
enable chap81
enable proxy
set timout 0
set ifaddr 192.168.4.1 192.168.4.13-192.168.4.27 255.255.255.0
set device /dev/cuaa1
set speed 115200
set dial "ABORT BUSY ABORT NO\\sCARRIER TIMEOUT 5 \
\"\" AT OK-AT-OK ATE1Q0 OK \\dATDT\\T TIMEOUT 40 CONNECT"
set timeout 180 # 3 minute idle timer (the default)
enable dns # request DNS info (for resolv.conf)
papchap:
#
# edit the next three lines and replace the items in caps with
# the values which have been assigned by your ISP.
#
set phone PHONE_NUM
set authname USERNAME
set authkey PASSWORD
set ifaddr 10.0.0.1/0 10.0.0.2/0 255.255.255.0 0.0.0.0
add default HISADDR # Add a (sticky) default route