I'd check the Ts and Cs first before deciding what to do next. I applied for a basic card and got my 20k miles. I then applied for platinum card a month or so later and my application was successful. I have recently received a letter stating that I am eligible for the additional 20k miles but I won't take that as a given until they have posted to my DC account!

Take a look at this thread http://www.flyertalk.com/forum/showthread.php?t=555281 for further info. on the subject.