Selling but dont deliver

They sold me blue karoake microphone i paid for it and waiting fir the order to be delivered after a month of waiting i sent them email they were telling me it was still packed its gonna be out soon for delivery all of a sudden they said its out of stock they will refund me money few days later i saw same blue karaoke microphone slling for big amount till today i never receives my money or karoake microphone please assist