From your 'My Hub' page (please see below)
If you go to the 'Menu' icon in the top right...
then select 'Contacts' from the options
Click the client profile followed by 'Assignments' from the list below the client profile picture and select 'Programs'
You can then simply click the program you are wanting to change
And in the top-right, if you click the pencil icon you can make the necessary changes.