Is it considered rude to reply 'It's alright' to something you are not happy about yet frown at the cashier?

It's a two-faced response. I would have also said it's alright, but I would have smiled. You just made the person feel like they didn't satisfactorily serve you. While that's true, the idea of saying "it's alright" is supposed to mean it was alright. It clearly wasn't! I think what you did wasn't good.

It was good that you didn't want to hold up the line. Since the cashier warned you that the soup wasn't very warm, you could have taken it to your table, tasted it, and brought it back to be re-heated if it wasn't hot enough.

You didn't have to accept cold soup, nor frown at the cashier. It was't her fault it was cold – she was trying to help.

It was not rude, but silly. You paid for hot soup, you should get hot soup. Managers can't fix problems if they do not know what they are. Asking for proper service (you paid for it) and slowing down the line alerts the manager or supervisor that the staff is not working properly. That is always a loser in the long run. Customers walk out and don't come back when orders aren't filled properly.

If you were going to lie to the cashier about your satisfaction with the soup being lukewarm, you should have smiled at her & let it go. Frowning can be taken as a sign of many different emotions or even physical pain. And people cannot read your mind, so you should try to say what you mean instead of hoping that they can take the extra time to guess what you really are thinking. The cashier was concerned enough to let you know the soup may need to be warmed up. If your food was cool, so would it be for the people in line behind you. I bet not everybody settled for cold food that day.

No it was not rude because you put others first before yourself making her job easier you said it was alright, but your body language said something different. That is not being rude at all. I would have given her the soup back and said no problem you keep the soup, with a smile. Perhaps you should go back in a few days pop you head around the door and shout to the cashier...Hey have you got any of that cold soup today its a great laxative, kept me on the toilet all night....and should I send the bill to this address from the hospital....haha

What you did was fine, not rude. It's unlikely it even made much of an impression on the cashier, but at least you let her know you were not happy without making a huge fuss.

You had a choice. If the temperature of the soup wasn't up to your satisfaction you could have said politely that it wasn't alright and that you weren't going to take the soup.

No, but you shouldn't say, "It's alright," if you don't know whether or not it is.

You could have smiled and said, "Thank you. If it's not hot enough, may I bring it up for you to reheat it?"

That way, if you didn't return, she'd assume you were satisfied and, presumably, you would have been. Otherwise, you could have it corrected.

You were passive-egressive. Either it was okay that the soup wasn't hot or it was not okay. Your show unwillingness to stand up for yourself and learn how to be firm but polite. You could have said, "Oh, golly, it isn't. Would you please heat up the soup or take it off of my bill?" Alternatively you could have accepted the situation and smiled.

Well, I think he/she might have thought it was either sarcasm or you were genuinly sad.I think since you didn't want to hold up the line nor make a scene it wasn't rude. That can be debatable for a nimbbr of people, just my experience.