We need the ability to change which SaaS Plan (tier) our clients are on.

For example, If they sign up for the first tier but want to switch to the second tier, we should be able to go to their account and move them to tier 2. Doing this should activate the tier 2 features for their account and switch their billing to the new tier's billing.

We would also like to have the ability to let user's change plans on their own, in the billing menu. This feature should be optional for agencies to use.