No, you don't have a right to the memory because you got exactly what you ordered. The cardinal rule with Apple is to always purchase the lowest memory configuration and install your own memory after-market. Besides the situation you have, Apple charges way too much for installing extra memory. I'm sure this would be fine for people who are afraid to even try to install memory, but it's so easy with Apple's machines, there's really no reason not to do it yourself.
Steve