Sign up voucher was invalid

I'm tired of calling your customer service and contacting your support team. Seems like you guys are only interested in getting people signed up but not helping , trying one last attempt to get my problem solved. I signed up in September and recieved a voucher code in October to be redeemed at virginactiverewards.com however everytime i tried it said voucher code invalid. I signed only because i was getting a voucher which i could have redeemed online but seems it was just a marketing gimmick. Kindly assist urgently else i will have no other option but to complaint further or even take it to ombudsman. The voucher code i received was 7ZIYUH. Nobody explained me about any condition associated with this voucher code, if there was any. I have been trying to get it solves since last two months and seems every effort is useless.