I have two type of subscriptions, Monthly and Yearly and I set a price for that. How can I change the price of Yearly subscription for a user already have Monthly subscription.
Example:
User with out any subscription Monthly price - $25 Yearly price - $79
User with Monthly subscription Monthly price - $25 Yearly price - $54
I want to change price like this. Is this possible through In-App purchase auto renewable subscription in iOS.
Welcome to stack overflow!
You could achieve something like that with subscription offers, but there is no need to do that.
The switch from one subscription to another doesn't necessarily happen immediately*, but at the next renewal date. So, if a user has a monthly subscription and switches during that to a yearly subscription, then the monthly will stay "active" till it expires and then the yearly subscription starts. So, after the yearly subscription expires, your user would have been subscribed for 13 months (one year plus one month).
*This doesn't apply when your subscriptions not only differ in duration but also in their service level. You can read more about upgrade and downgrade of subscriptions in the Ranking Subscriptions Within the Group section of this article from Apple.