extremely poor customer service

I purchased a c***** super M milkshake yesterday as I usually do and after taking a sip I realised a funny taste in it so I checked up the expiry date was for next year but the milkshake was tasted like it was spoilt so I decided to email c*****s customer care this morning notifying them about the situation and the whole day passed I never got any feedback I am really dissatisfied as c***** is known to be a big company