Online Vouchers

We received an online bought voucher in December. But when we went to the Fourways Crossing branch to spend it we were told we couldn't use it there. When we asked the manager why, he tried to get smart and said that it says on the voucher that it's meant for the online store. But all it says that it "can (not must or at the very least can ONLY" redeem it in the store and then gives the URL but not once does it even specify ONLINE store.

So we left and ordered online when we got home, only to find out that we can collect the order from the very branch that we were told we couldn't use the voucher at. We would presumably also be getting the product out of that stores stock anyway so why could they not just verify and let us use the voucher when we were there to begin with?????