> something do you have to redirect stdin and stdout to /dev/tty00?

The problem you might be having is that you have to set some flags using
stty for this to work...it took ages for me to get it going.  It's a lot
easier to just get pppd to call chat, because pppd will do the required
magic.  (ISTR it's something to do with the CD line...which won't be
active until the modem connects, but the computer won't talk to the modem
without it, unless it's explicitly told to ignore it.)

If you really want to talk to your modem, I can recommend minicom...it's
in the pkgsrc tree.

HTH,

David.