A Mosaic agent (if you contact them over the phone or through the chat) may be more inclined to make this change for you (and if you google this exact scenario, there are many reports on other sites that Mosaic agents have made this change for them) because it's not specificaly allowed or disallowed. A regular agent at the airport is hit or miss, but if they see that you are a Mosaic, they may be more inclined to do it as well.