Add apple watch series 9

I recently took up a new line with Vodacom and the order is currently sitting on back order due to stock unavailability, and for the past 2 days I have been struggling to add an apple watch to the order, I am looking at the Vodacom world magazine and I see that I can add the watch for R339 a month for 36 months..(Apple watch series 9, preferably white or grey) can someone please assist me with that please