Bank gave provisional credit on dispute for three different transactions totaling $150. One merchant then issues refund for one charge in the amount of $100. Bank reversed provisional credit for the full amount, $150. Shouldn't we have only reversed provisional credit for $100 and made the other $50 of provisional credit final (based on the outcome of our investigation)?

Sounds like it - you only officially resolved $100 of the $150 dispute unless you denied the portion that made up the other $50.

Thanks Randy, just wanted to be sure I was thinking through this correctly.