Repeat the ping tests such as below, aborting with Ctrl-C:
---------------
$ ping 206.47.20.85
PING 206.47.20.85 (206.47.20.85): 56 data bytes
64 bytes from 206.47.20.85: icmp_seq=0 ttl=51 time=169.5 ms
64 bytes from 206.47.20.85: icmp_seq=1 ttl=51 time=170.1 ms
64 bytes from 206.47.20.85: icmp_seq=2 ttl=51 time=170.1 ms

$ ping corel.com   
PING corel.com (206.47.20.85): 56 data bytes
64 bytes from 206.47.20.85: icmp_seq=0 ttl=51 time=169.1 ms
64 bytes from 206.47.20.85: icmp_seq=1 ttl=51 time=169.9 ms
64 bytes from 206.47.20.85: icmp_seq=2 ttl=51 time=170.0 ms
64 bytes from 206.47.20.85: icmp_seq=3 ttl=51 time=169.9 ms

If the numerical address 206.47.20.85 succeeds, while 
the same named   address corel.com  fails,
It is Only a DNS problem.

If your IP 
1) dynamic assigns DNS addresses, then add into /etc/ppp/options
  usepeerdns
2) provides  static DNS addresses, use Mandrakes dialout configuration
utility
(kppp config tool?) to have the address added to appropriate places in
the /etc/ppp/ tree
or in /etc/resolv.conf

On my Debian system:
$ cat /etc/resolv.conf
  nameserver 207.172.3.8
  nameserver 207.172.3.9
is copied in upon CONNECT from
  /etc/ppp/resolv/rcn
but this varies with different Linux distros.

Also before starting a PPP session:
# ifdown eth0
or
# ifconfig eth0 down
as any DNS service set for ethernet will be tryed for PPP,
usually with failure unless you have a sophiticated setup.