We had Fiserv reach out to a customer about some activity on her account.
She then called us and said at the end of March her car was stolen, then her purse and phone were stolen a few days later (she hasn't informed us previously).
She isn't sure which transactions are fraud and which are not. We have asked to her to go through her statement to determine which transactions she would like to dispute. Do we wait to start the investigate until we hear back from her? We aren't sure exactly what we are even disputing at this point.

Thanks in advance.

You don't have the information that triggers an investigation yet. She does have to identify the transactions she is challenging or questioning. You do, however, have enough to go ahead and shut down her debit card to prevent any further unauthorized transactions.

Thank you, and we did shut down her card.