well here's a quick overview
dial up script needs:
isp phone number
username
password
modem device(usually a com port-->/dev/cua0 for example
modem itself needs to work and have appropriate drivers if needed
some modems also need an initialization code to dial up, often its "atdt", and thats often part of the script
once a connection is established a daemon called pppd starts and maintains the connection
as I recall the pppsetup script usually works ok in slackware,some isp's need specific things, have no clue what netscape wants, check their website
slackware has a manual at slackware.com, and there may be docs in your /usr/docs directory
also,
http://www.tldp.org has how to's, without more info about exactly whats is or isnt happening I cant help you much