BIRTHDAY VOUCHER

So, I received a voucher for my birthday on 4th July. On the app it says my voucher is valid for 45 days from date of issue. Yet, the voucher expired on the 20th July. Not the head office customer service, nor the branch I normally frequent, Constantia Village, can explain to me how they get to 45 days from the 4th July to the 20th. I will NEVER buy anything from this company again. I won't even buy their cakes that are in some stores.