You have to delete the ifgroup inorder to change the mode. There is no option to change the igroup mode. As ifgroups are in broadcast domain and they have lifs, you were not able to change them. Please use the below process in order to change them.
1. Delete the lif
Network interface delete -vserver svm1 -lif lif1
2. Remove the ifgroup from broadcast domain
network port broadcast-domain remove-ports -broadcast-domain Data -ports node-01:a0a -ipspace Default
3. Remove the physical ports from broadcast domain.
network port ifgrp remove-port -node node01 -ifgrp a0a -port e0c
4. Delete the ifgroup
network port ifgrp delete -node node-01 -ifgrp a0a
Now you have to create a new ifgroup.