Membership/Subscription - Member/User Change-Up or Downgrade

We offer a monthly or annual option for our program - to have someone switch, we have to do this manually, which also means having to receive an email and then do the steps to do that (and not have a great record they wanted to change).

We would like to see an option where the Customer Center could have a manage subscription option so someone could upgrade/downgrade their level - this doesn't just work for monthly/quarterly/annual, but also those with levels of service on plans.