Action against accident causer not paying Bill but bike details known

Hello ...can you please help me ..i wants to know ..What should i do .. On 31st dec,2017 ,new year night some guys hit my car by a bike and they assured me at that time that they will give me all money that will be came for repairing and than i trust those guys and i gave my car to service center ,now these guys refusing to gve money by not picking phone and cut my phone and than i go to police station regarding this..police man saying we can't do any thing as your vehicle is already repair and you don't have any written evidence that they will give money back but i have whatsapp messages with one of those guys on which he was saying we will give money after repair and policeman saying its not acceptable.. can anyone suggest me what should i do ..thnks in advance I already take my insurance but still i have to pay other than insurance. I take photographs on that night of his broken activa i have those photographs and phone recording that they will pay mo