Users are manually changing their subscription offer after experiment presented them something else

Hi there!

Have somebody experienced this? Is there a way around it?

What happens is: 

1. user is presented with a paywall (through an experiment)
2. user go the iOS settings/subscriptions and then change their subscription, effectively choosing the cheapest option (since they can see all in app purchases there)

Is this normal? Is there a way around it, to prevent the user from changing their originally presented offer through the A/B experiment?

Thanks!