Cabanas Sun City Discount Did not apply after booking

I placed a booking with Cabanas reference ARWZRNR and should've received a 10% discount by subscribing to the news letter which I did. The 10% discount did not apply. I emailed *** to enquire and when called back they advised I did not click the right button and the only way to resolve is to cancel my booking and start over. The prices however have gone up quite a bit since I booked and would not make sense. Is there no way a note can be added to the system whereby it can be deducted from the system when we arrive?

Kind regards Gary Madden ***