Funkifized - go to File > Import > Import Melody from MIDI File, then choose your MIDI file. You'll get the Import MIDI window - in here, please unselect Include Patch Changes - you can see that in the screenshot I attached. This step is necessary because your MIDI file includes a Piano program change message in it, and this message can override the setting in BIAB.

Next, if you imported the MIDI to your Melody track, go to the Melody menu and change Track Type to Single Channel - as your MIDI file has two tracks in it, this tells BIAB to default to using Multi-Channel mode, which by default uses MIDI channel 4 for patch changes while your MIDI is on channel 1.

You should be able to change patch now.

Attached Files (Click to download or enlarge) (Only available when you are logged in)
MIDI import patch changes.png (27.33 KB, 58 downloads)
I work here