The big E icon in top row.
Event List
You want to find any program changes as Mario and Bob mentioned.

You can either remove them, or change the number to the patch you want it to be.

They are usually at the beginning of the song, so rewind before opening the Event List.
As Mario said, they may all be on different tracks (example - for each MIDI channel), or they may all be hidden on one track.

Another option is to blindly Cut all program changes.
To accomplish:
Highlight all tracks from beginning to end.
Click Cut icon (or CTRL + V)
Enable Data Filter (!important)
Hit Enter
In the data filter deselect everything but Program Changes.

Cut 'em (Enter).

Remember there is an Undo button if you goof anything up.

Make your sound your own!
.. I do not work here, but the benefits are still awesome