BuySmart WhatApp Rewards program

I have been using the Tiger Brands BuySmart WhatApp Rewards program.... I claimed a voucher 3 months and I found out the Voucher code is invalid ...m I have been trying to get help to sort this out with the company that gave me the voucher but no communication from them .... I have send e-mails , twitter direct msg , Facebook msgs, called the office n still no luck