Deceiptful business practice on promotions

Roman's Pizza has a seasonal special where you can buy any two pizzas and get a free 2L Pepsi for R199. I ordered this pizza online (#***), like I usually do, on the app. My brother picked up the pizzas (as he was on his way to me) but never received the Pepsi's! He didn't know about the special. I phoned the branch and they simply stated that if I do not select Pepsi as an extra then I won't receive the Pepsi's! What BS is this? They claimed that if I selected the special the Pepsi would have been added...yet the app didn't ask me (nor should it as it is an added extra...NOT OPTIONAL!!!). Don't you think that the app should stop my order from being processed if this selection should be made??! From what I'm seeing this is **** from Roman's to ***** the free Pepsi from unknowing customers! The best part is...if you go to the order history it doesn't indicate a special, ONLY the pizzas that was ordered. I verified this to be the same with the usual "Sava Flavor" specials...it only shows the pizzas selected, not that a special was ordered! I'm not happy with their desceipt! If this is how they want to do business they have just lost a regular customer!