It manages the customer data for the transaction. Although the transaction is managed by AltaPay, you (the merchant) can style the customer facing pages so that they appear to remain within your shop throughout.
You can also do a variety of back-end calls directly from your own system. This means that you can set up automatic processes for capturing goods when shipped from the warehouse, for refunds when goods are returned, running a custom report, charging their subscription payments and so on.
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