refusing to handover goods

Samuel Musekwa is a cab driver at Uber. In April 2015 I left my sub woofer speaker in his cab and he said he will take Care of it. I have been trying to get it back but he is giving me the run around. I have tried to make arrangements with him more than 4 times, either he says he is busy or he will get back to me which he never does. I have even suggested to come pick it up instead of him driving, he still refuses. All I need is my speaker back, I have wasted too much airtime and petrol trying to get my speaker back, can you please assist