FTC Complaint form. I'd think the FTC would be better in the long run than the BBB (although you're more likely to get a *personal* response to BBB, in my experience, FTC complaints put it on the government's radar and if the rumors are true that the FTC is already investigating Gamestop for these practices it's a good thing to add more experiences to show this really is a trend)

https://www.ftccomplaintassistant.gov/