We are using PayPal subscriptions to automatically make ongoing monthly donations. The user initially creates a subscription with some pre-determined monthly donation amount (e.g., say $50/month). This creates a recurring subscription which we process by way of IPN. All good there. But, our interface allows the user to come in and change their monthly donation amount, say from $50/month to $100/month. I am wondering how I can change the PayPal subscription to reflect this new amount?
There is a method in PayPal's NVP API called "UpdateRecurringPaymentsProfile" which says I can update the subscription amount, but unfortunately it says:
For recurring payments with Express Checkout, the payment amount can be increased by no more than 20% every 180 days (starting when the profile is created).
To be honest, PayPal's API's are quite confusing so I'm not sure if I am using the Express Checkout or not. (We are creating Subscription buttons using the simple Website Payment Standard API).
Will this work? If not, is there an alternative to achieve what we need?
Thanks!