Incoming calls to my work number

Good day,

Can you please assist me in incoming calls that were made to my work number in July 2017? We have contacted many branches and no one can seem to help. We have received phone calls to our work numbers and people are trying to cause trouble for myself and my husband.We would like to know who called the work numbers.We have written permission from the Directors of the companies to receive the incoming calls made in July but no one at telkom can assist.

Please assist me with this query.