Please make sure the file /etc/ppp/options exists.

You need to install:

        ${X11BASE}/share/examples/xisp/ip-down            to /etc/ppp
        ${X11BASE}/share/examples/xisp/ip-up              to /etc/ppp
        ${X11BASE}/share/examples/xisp/peers/xisp_modem   to /etc/ppp/peers
        ${X11BASE}/share/examples/xisp/peers/xisp_dialer  to /etc/ppp/peers

and make sure they are executable for user "root" and group "dialer"
to be able to fully use this package.