End user access to upgrade billing

On behalf of one of my clients, i created an app and now i'm giving the users access.

I'm the standard user on the account, i developed the app and also set up the end users. They all have limited access to only a certain app. I also added their billing info and set them up on the monthly billing plan. However, they may want to upgrade to annual billing on the plan.

Is there a way for an end user to do this, or am I only available to do so as the "standard user."

Kind of odd if not, as I only have relations to their product as the developer, i don't need to be involved in their billing.