Paya - turn off extra pop-up receipts when processing a payment?

We have a long time customer who has been using Paya for years, and now (due to an ownership change) they are moving from Chase to Moneris, so we've set up a new Payment Type with the new Merchant Account details.

When we process a payment in the new payment type everything works normally (in Cash Receipts Entry, Sales Order Pre-Auth...), except at the end of the submission, when the Auth details are returned, there are two pop-up web pages (one for "Merchant Copy" and one for "Customer Copy") which we don't want. 
Example (with sensitive details hidden).
Inside Sage the two Payment Types are identical (except for the merchant account information) so it doesn't seem like something we can control. 
Does anyone know how to disable these pop-ups?