Ticketmaster Justin Bieber refund

I am still waiting on my Justin Bieber ticket refund. The concert was cancelled in September this year and you cannot get hold of anyone to get a refund. In the meantime my tickets have been misplaced and all I have is the proof of payment. Please can you help me. I bought 3 tickets and Ticketmaster is ignoring my requests. How many are still struggling to get their monies. This is not fair.