I tried deleting and adding new recipients in the form but it says I must upgrade in order to do it

I have an existing form with 23 recipients set up in the form settings. I deleted a few names and wish to add a few more but it says I must upgrade t

Yes, free accounts are now limited to only 1 recipient in the form. You will need to upgrade in order to add more. But note that existing forms on free accounts with multiple recipients will still work, we kept them. 

If you wish to add more without upgrading, you will need to create a new notification email. One recipient per template.