Why does my preview survey charge shipping charges?
All survey previews are done through a fictional test backer, which shows up as "Test Backer- John Smith". John Smith's default settings give this backer full pledge credit, but $0 in shipping credit. As such, every time a survey is previewed, unless the shipping charges are adjusted from the Creator side, the survey will show a debit in shipping charges, and you'll be asked to pay shipping charges in the checkout.
To adjust the shipping in your preview survey:
1) Click on the Preview Survey tab on the left hand side
2) Update the Pledge Amount to be both pledge reward + shipping charges
3) Hit Preview Survey