This article is from the Credit cards and Consumer Credit FAQ, by adams@spss.com (Steve Adams) with numerous contributions by others.
You don't have to pay them while the bank is investigating.
When the bank credits your account, they are also supposed to credit
your account with any finance charges that were assessed on the
disputed amount before you wrote to them. They may or may not do
this without further prompting from you.
Again, if the disputed charge is later found to be correct, you will
have to pay finance charges on it.
 
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