No reply on request to reverse transaction

Attempted to purchase a voucher through the Multiply online shop.<br> Amount was credited from my account but even after waiting 3 days, as the call centre agent advised, did not receive the voucher. <br> Multiply now say there is no record even though I sent through a document from my bank of the authorisation of the payment. <br> Even if the voucher is no longer available I would like my transaction reversed.<br> Currently nobody is replying on any of those mails.<br>