Coca cola......totally flat

I bought a 2litre coke....totally flat....was sealed still.....I let it go because it was only 1 bottle and dont see the need to complain......after 3 weeks I bought again a 2litre cioke......still sealed.......and i heard a sisssss sound....and do inspection...and itnis 1 of the cokes a bought that release the gas.....I send an email to *** 2 weeks....no reply from Coke....this is a waste of money.....if you do have money to throw away...buy coke...