Incorrect quantity in the cans

I would say I buy approximately 48 cans 250ml of redbull original on a weekly basis.

I noticed on my last purchase that 2 can was about 100ml only. I called redbull/sent and email , they pitched up at my door with 4 x 250ml light blue cans. That was not the apology I wanted. I can afford to buy my own redbull Firstly, how did the can pass checks without the correct quanity, dont you have quality control procedures. How many of the cans actually have the correct milliliters in it.

I want to carry out my own investigations to prove my point. Want a representative present.