His debit card ended up declining it anyway, but that's not the point. The point is Google thinks he owes them thousands of dollars, and a collection agency is hounding him for the money.

Disputing a charge with your credit card company doesn't change that. The credit card company might side in your favor and reverse the charges, but the original company can still pursue payment with you directly. Their claim can even show up on your credit report. I remember working with a payment processor in Europe that even automated sending a bill to collections if it was charged back by the consumer's credit card company.