Glitch in system resulting in product out of stock despite paying

After ordering and paying for products online, I get an email that there was a glitch in their system and 2 items are out of stock. I chose to get an online voucher which when using it, there was an issue with payment, the order got cancelled and never went through but now I can't use the voucher. They do not answer their phones and are difficult to communicate with on email. Now I'm not sure if I will get my money back or not!