FLAT COKE ZERO

I was en-route to Jhb stopped and purchased a 500ml Coke Zero at the N1 garage, on opening discovered it was flat. Whilst in JHB we purchased 2 more 500ml Coke Zero and they also where flat. I complained to Coca Cola and they in turn gave me 4 x 500ml Coke Zero. Wow when I opened the first one this was also flat, I opened the second one this too was flat and it would expire in 3 days time. I again complained to Coca Cola and now nobody says or does anything its all gone quiet. This has been with their complaints depart for almost 2 weeks.