[Koha] Different call numbers, same item

Hello there, I'm hoping someone can help me - I need to run a report to find item records that have multiple items at different call numbers... Eg: one branch will have a title at a certain call number, and after merging records, there is now a second holding at another branch, but at a different call number to the first How can we identify these records? Any help you may provide is much appreciated. Thank you, Kerrie Harvest Bible College Library