Notice of Dispute Page - Spinning, No Submission

Does anyone have any luck submitting a dispute?  The page keeps spinning after I include my supporting documents.  

I was told to file a claim with USPS by the AT&T supervisor I spoke to after the customer service agent send me the label to use for my return and the package was tampered with and items stolen.

I did file a complaint with BBB but wanted to cover all basis since customer care told to me that there was no escalation process on their end, and the supervisor was the last person I would be speaking with.