Best practice for "Trial Offerings" vs "Immediate Offerings"

Hey team, consider the following scenario: 

1. User Signs up. We show them an “Initial Paywall”
   1. Offerings: $20 month, 2 week free, $80 a year, 2 week free
   2. Here, we let the user “Skip” the Paywall
      1. In this case, we don’t show it to them again, for 2 weeks
2. _2 weeks later_. We show the user a “Blocking Paywall”
   1. Offerings: $20 month, $80 a year

Some users buy at “Initial Paywall”, some users buy at “Blocking Paywall”. 

3. 3 months later, the user goes to their “Membership Settings”
   1. We want to let the user upgrade / downgrade
4. Here, their `activeSubs` could contain _either_ 2 weeks free, or not

Problem:

Let’s say in the upgrade / downgrade, I have “$20 a month”, “$80 a month”. A user on the “20 a month, 2 weeks free” _can theoretically “upgrade” to the $20 a month plan. This feels like a bug, as it won’t make a difference -- I would like it so they can only upgrade to the yearly one.

Is there a “best way” to handle this scenario?