Help with turkish sim and SMS problem (Istanbul)

I'm unable to send SMS to only one specific number/phone, which is my brothers, and the most important person for me to be in touch with at the moment. We're both in turkey, he is on a turkish phone and me on a foreign phone (iPhone 4s) with turkish sim. My phone has been successfully registered and been able to send and receive calls and texts to everyone else (domestically, in turkey that is) I can receive texts from him, but not send. Upon a little research, it looks like his area code Protected content specific to Vodafone and not an actual area code? I'm thinking maybe his area code is seen as international so my domestic sim won't send to him, but that doesn't explain why I can call him. Is there any situation between Vodafone and avea that might be the reason? Trying to avoid buying a new sim/phone for only being able to text on person, very frustrating.