Vitality rewards - Kauai

I am a Vitality member, and joined a new movement from Discovery called Vitality Rewards. By completing certain fitness goals you are entitled to a free coffee or smoothie from Kauai or Vida. Upon registration I received my first voucher and attempted to use it on 3 October. The staff at Kauai in Little Falls unsuccessfully tried to load the voucher, but their system didn't allow it. I paid for my smoothie. I reached out to Vitality in an attempt to resolve the matter as I feel I have not received what was promised. Their responses are very slow, and eventually let me know that the voucher was already used by me. I responded to them again by forwarding them my proof of purchase and payment showing that I had not used the voucher and was made to pay at the counter. They have completely ignored my response, I have had no interaction despite their auto response email saying I will be contacted. It is more than 48 hours now. Their service and response time is absolutely pathetic.