If you are having issues with both Siri and iMessage... that might suggest that you have not entered contact info correctly. Siri might also have a problem with your accent/dialect. Siri is still in testing phase and does not recognize all languages from what I have read.
I do not have Siri, but if you do a search on this forum for this issue, 9 times out of 10 it's because the contact info is incorrectly entered. Sorry I can't help more. There was a thread just recently for this same issue.