Most of the time, there is no need to use a bps above
19,200bps.  Unless the data is very structured or has lots of
empty space (database or spreadsheet) the compression won't get
you over 19,200bps.  When the modem refuses to work above 19,200
or doesn't work well, it is usually hardware on the computer
(slow serial port or some other conflict even on a fast
computer).  Set the software and dialing directory for 19200.
Make sure CTS/RTS flow is=ON.  And locked DTE (baud/bps) rate
(software does NOT follow modem connect speed).

    On the other hand, never set the modem BELOW 19,200.  If you
get a 12,000 or 14,400 connect the software and modem may not
speak to each other correctly.

    The phone company claims the bandwidth of the phone lines
will only support 9600.  Most of the time, from many locations we
know from experience that often 14,400 or 12,000 can actually be
achieved.  However when the connections for whatever reason won't
support the faster speed, it should come as no surprise.
Sometimes you can force a higher than 9600 connect, and get some
(or a lot) of garbage characters.  When the connect is TOO poor,
the modems often will not even stay connected.  In such a case
use one of the 9600 dial prefixes (insert or pp11-7 or 10-7).