Check the note under Subscription pricing:
https://developer.android.com/google/play/billing/billing_subscriptions.html#administering
You cannot change the price. I guess that it is the same for the renewals.
You will need to create a new product for new customers.
Thanks
@Erel for your reply. Now this point it's clear for me.
About "old" customers with the old subscriptions I have only one doubt that I explain belove:
1) MY ACTIVE IN-APP PRODUCTS
sb001) Subscription with annual renewal with x price
sb002) Subscription with monthly renewal with y price
2) CURRENT VERSION OF PUBLISHED APP
The actual app code, check if the "sb001" Subscription is payed using BillingManager3 APIs and if it not paid than raise the payment / subscription GUI.
3) NEW APP VERSION
The new app code, use the same check logic but it should check if the "sb002" Subscription is paid.
Within this scenario:
A) new customers install the app (3- NEW APP VERSION) for the first time and the users subscriptions point to the sb002 Subscription with the related renewals (this is OK).
B) The "old" Play Store users (that have the old app version installed that handle sb001 subscription) update the App to the new version and the app start check for the sb002 subscription (check to verify that subscription is paid).
This is my doubt: What happen at the "old" users that have an active (sb001) google play subscription ?
Actually I don't known how to handle this point correctly.
Thanks in advance for your reply.