iMessage can't see some of my contacts
I have iMessages activated, I know it since I can use it with many of my contacts who owns iPhones and also have iMessages and we can contact each other without problems, I'm also using Mountain Lion and I can message them using my Mac.
The problem is that I have other contacts which I can't see, I only have the SMS option, one of them is a colleague and I see him every day in person, we've tried to message each other but it just won't work. Green messages instead of blue.
We've tried reactivating iMessages and everything you could try.
The same contacts my iPhone can't see, on the Mac I can't iMessage them either, but those I can iMessage on the iPhone from my Mac works well too. Same contact, same situation on both platforms.
Is there anybody else suffering the same problem?
I'm from Chile.
Thank you
Claudio
iPhone 4S, iOS 5.1.1, 32 GB