About subscription price changes

Alongside our most recent release we are planning on updating the subscription prices of all our old products to reflect the new pricing model. This most certainly results in price increases of over 50% for the majority of our old subscription products. As such, those customers of ours that are still subscribed to these old products would need to give their consent for the new price moving forward. Our app uses Unity IAP and StoreKit 1. StoreKit offers a function called showPriceConsentIfNeeded, which seems to be exactly what's required. Sadly, Unity IAP does not offer a way to ask for user consent in cases such as these. Also due to Unity IAP, we also have no easy way to call showPriceConsentIfNeeded manually. How would StoreKit 1 handle the price increase in this case? Would the subscription automatically end at the end of the current billing period, or would the user be informed of the new price via some other way - such as an e-mail or a push notification?