So far PayPal tech support has been utterly unhelpful. Taking days to reply with a message like "upgrading subscriptions more than 20% was never possible" which is clearly untrue, denying it even when provided with screenshots of actual upgrades. Since our business very much depends on users being able to upgrade we've just completed the transition away from PayPal for new customers. We went with Braintree, a daughter company of PayPal, because they can actually do PayPal subscriptions with normal upgrades again (without the customer present even!), and also restores the ability to retry a failed subscription three times instead of halting the subscription on the first failed payment (seriously, who thought that was a good idea?). The API of Braintree is very different, so you are going to need some serious programmer hours to redo the integration, especially if you (like us) don't want cancel the existing customers and thus need to support both APIs. The integration is not a smooth as a new player like Stripe but Braintree's tech support is a dream compared to PayPal's.
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