Wonder US Property Group LLC review: Unethical behavior... Theft

We went into contract with Wonder US Property Group LLC to sell our residence. We were under contract when the "Realtor's Lock Box" was placed on the front door containing the entrance keys. We were assured that our personal property and contents would be secure, as any third party contractors or buyers would be escorted by a Wonder US Property Group employee and that they would maintain a list of the date, time and who entered the residence.
During the time the residence was under their care and control, thefts occurred. Now, the company has refused to respond to letters and email request to provide a copy of "when and who entered the property and the name of the employee who allegedly escorted them. The Company has also refused to provide the name of their Insurance Company so that we can file a Theft/Loss claim.