Note that TXD is the data to be transmitted over the GSM link - so it is an input to the Fastrack;
Similarly, RXD is the data to received from the GSM link - so it is an output from the Fastrack.
This is explained in one of the linke I cited before.
That’s not what it says in the Fastrack Manual, is it?
The default is that the Fastrack requires RTS and CTS - SO You would have to explicitly reconfigure this with AT+IFC
Alternatively, build a loop-back into your connector - see: viewtopic.php?f=3&t=419&p=3498&hilit=+loops+back+rts+cts#p3498
See also: viewtopic.php?f=53&t=1958&p=7277&hilit=loopback+rts+cts#p7277