I would like to seek advice on how to deal with this problem.

Back in July 2016 I send $10,000 to a mortgage broker for the due diligence and appraisal fees for a block mortgage of 8 properties. He apparently sent the money on to the mortgage underwriter who were going to process everything for BlackRock who were the lender. Now I find that the mortgage underwriter has stopped dealing with BlackRock, and he won't return my money because it has been spent (although there is no evidence of what it was spent on). The underwriter is also not picking up the phone or answering his emails.

Does anyone have any suggestions for how I can get my money back?