Login as user;
su - root
ifconfig ppp0
You should see two ip addresses.
Did you add you DNS server name for your ISP to /etc/resolv.conf?
if not
edit /etc/resolv.conf and add them somethng like this:
------------- /etc/resolv.conf -----------
serach you_isp.com
nameserver 111.111.111.111
nameserver 111.111.111.112
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