Characters are being hijacked in Twitter SMS updates

@ [At-sign] sign becomes ? [question mark] in inbound Twitter SMS notifications.

And _ [underscores] become upside-down Vs.

This only happens with SMS from Twitter - i've confirmed with my carrier and friends that I can both send and receive

I have an iPhone 3G on Rogers in Canada.

I have done the following to try and resolve the issue. None have been able to fix the problem.

1. Reset mobile notifications on twitter.com
2. Confirmed language and region settings are correct on phone (English, etc)
3. Restored iPhone to factory settings
4. contacted Carrier to confirm if anything was wonky with my account - they have been able to test and confirm everything is working properly

Please help! This is really irritating....