Tim is correct, you can not use the IA switches to program change only CC changes.

having said that you can set up the GCP in two different ways…

1. 8 IA switches and 4 Bank Switches (IA sends MIDI CC and Bank Switches send MIDI PC)

2. 12 Bank Switches (12 switches send MIDI Program Changes)

To allow you to switch phaser on you will need to send a Program Change, so you could set up all switches to Bank Mode which will send all Program changes.

It depends on what you want to do.

The way I use it is that I use the 8 IA and 4 Bank mode, i figured out that instead of having 1 of the Banks per song, I get a lot more flexibility if I set a group of banks per song, rather than just the one.

I use a set of 4 Banks per song / setup so I have the option of a intro, verse, chorus solo ..type of thing.

I usually setup the first bank to be the main sound of what I want, then I copy these bank settings, names etc to the other 3 banks in this group of 4, then I edit them as I want for different sections…some songs are all the same…some different.

so…

Banks 1 -4 song A

Banks 5-8 Song B

Banks 9-12 Song C

Banks 13 – 16 Song D

this allows me to send Program changes within a Song

so Bank 1 Might set Axe-FX Amp AC30, TimeFactor 3:1 and Space 1

Bank 2 might only change the TimeFactor to 4:1

You can still use the IA switches to set tempo, bring tuner up on a screen bypass effects etc…things that use MIDI CC's rather than program changes

etc

So you maybe able to do something like this to achieve what you are after.

hope that helps.