I don't know which company, and if don't know whether you're talking about telephone customer services of face to face customer services, nor do I know the specifics of the customers complaint.
But if a company chooses to treat its customers like cunts, and you choose to accept pay to represent that company and tell a customer that the company you represent is intentions to treat him like a cunt, you have a right to expect to be treated accordingly.
You are cannon fodder, there to take the flack. That is your job, and you accept rename ration for backing up and reinforcing the company you represent's moral position of issues. When people take issue with your moral position, you have to either have the spine and the skin to take it, or defer to someone more senior.
As I say, without knowing the specifics of the case, it's hard to say. But I have been in situations in the past where a company has been quite clearly wrong, and their way of trying to deal with it is to put someone in front of me with neither the intelligence not authority to resolve an issue. If that person in effect is only going to say, 'sorry madam, but I don't make the rules, you need to write to PO. Box XYZ', and 'no you can't speak to my manager, she'll just tell you what I've told you', then she is being deliberately obstructive and belligerent, and will be treated exactly as she deserves to be treated, even if it means making personal complaints in writing about her demeanour and refusal to deal with an issue or pass to management. At least then. I know that letter will sit on her file for her career with that company.
If a company is going to screw you over, and you can't get the staff in front of you to bow down to senior management, you can at least scar the careers of those in your way.
As I say, I have no idea if your talking about a guy complaining about a cup of coffee, or an insurance company refusing to abide by the contract, so I have no way of knowing. But you are where you are for one reason, and that is to take the shit thrown at the company. Provided that doesn't come with physical threats of violence which is against the law, you are fair game. It is what you are paid for, whether you care to like it or not. Grow a thicker skin, or find a company who cares more about its customers.
As peoples' spare money declines, it becomes more valuable to them, and companies become more and more desperate to keep ahold of it once they've got it, so expect more of the same, and worse as the economy contracts. Or pick a more ethical job.