[Koha] Call number is present in item records but not displaying on OPAC

Hi All I have imported a records from an Excel file to Koha. My major challenge now is that call numbers are aappearing on the item record. However, when I open the item record for editing in cataloguing module, the o - Full call number has the call number already has the call number and when I save the record the call number them appears. I have close to 90 000 item records. It would be difficult to open all the records and update them. I will appreciate any hint on updating the records. Regards, Admire Mutsikiwa University of Zimbabwe