DVD writer and DVD burner are synonymous. Writer is more the technical name, while burner is more commonly used in the spoken language (especially on forums like ours).
If you mean that you thought you bought a device capable of creating DVDs and it turns out to be only capable of creating CDs (don't know if these are still sold though), then you are out of luck.
But as deanimator asked, what is the brand and model of the device you bought (it may show on your receipt). That would help us determine what kind of device it actually is.
ps greetings from Madrid...only visiting though