Which Platinum are you talking about? What country?

Next: What are the specifications of their network and how do they compare to the types of networks supported by the N900?

2G Network GSM 850 / 900 / 1800 / 1900
3G Network HSDPA 900 / 1700 / 2100

Also: Google might be able to answer your question much faster than applying for a board like this and waiting for someone to clear things up.