1. Check all the cables, especially from modem to phone jack.
If necessary, replace the modem-to-phone-connector cable.
2. Make sure the modem is attached to /dev/ttyS0 or some such. "/dev/ttyLT0" does not seem correct. To do this, restart the "setup" program, as root, and enter the correct information for your modem:
http://www.slackware.com/book/index....urce=x209.html
3. Test modem with a specialized program, such as minicom. Try dialing out and see if it works...
4. If all else fails, test your modem on another machine...
Hope this helps!