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so it sounds like ultimately, you want a workflow where you can proceed with purchasing the item with various different credit card numbers. 

I would suggest creating a csv file with a column header "credit card number" and then filling out the subsequent rows with  various different credit card numbers (i.e 1234 5678 9101 8013) 

And then using the "make data loop" option, you can data drive your workflow by essentially parameterizing your credit card number value to be entries from your csv file. (https://support.smartbear.com/testcomplete/docs/keyword-testing/basic/data-driven-loops.html)

In the end, what you have is the same workflow where you buy a product, but iterated multiple times over the entries in your csv file, so that you end up testing the purchasing of a product using multiple different credit card numbers.