Disappointed Clicks Customer

I have always shopped on clicks online aswell as the store and I have never experienced any problem,however on the 23rd of November 2018 there was an online special where I purchased a lip gloss off 149 and I was supposed to get another free.,sadly I did not receive the free one because it was out off stock. On the 1st of December 2018 I received a mail from ********** asking me if I would like a 200r online voucher or for the money to be deposited into my account. I rep**** saying I would like the online voucher. I did receive a voucher off 200r.,but when I tried to retrieve the voucher to purchase a product it is invalid, it keeps giving me the same message that my product has exceeded the limit,which is not the case because the product I want to purchase is 144.95 with or without delivery charges it will come to 200r or less. I sent emails to clicks several off times and nobody even bothers to reply,calling the call centre and nobody answers. And BTW the voucher is only valid for 30 days.