Coupon code not applied at checkout. Got charged double

Got charged double on my recent order. When I called in to support, they said that my coupon hadn't been applied at checkout but that they would apply it and apply the refund back to my account. When I received my equipment, the receipt had record of the coupon that was applied upon checkout. Unsure how I was charged the full amount but the receipt would indicate otherwise.

No big deal, they said it would take 1-3 business days to receive this and it has now been over a week.

When I try to call in now, I am left with one ring followed by silence and then followed by a complete disconnect.

Who can I contact to resolve this issue as soon as possible?