Unsatisfactory service

Firstly, i was buying jumbo chips with Russian and Vienna, coz i was thirsty i decide to sprite 300ml Coke has priced it R7 and they sell it for R11, i find it a bit unfair even if they want a profit they could at least sell it for R8. I believe there's somehow they get their profit.

Or should i email coke to lodge my complain. Another thing their Jumbo sized chips it like a medium sized. Their chips are often burnt. I will keep the receipt safe as proof of purchase for further complaint to Coke.