I am trying to text someone who has an iPhone 3gs and is on a firmware 4.x.x. Whenever i try to text him it says "(phone number) is not registered with iMessage" and i cant hit send after i type out my message. I tried disabling iMessage in settings, but when i go back to the Messages app it want me to set it up again and i cant just say no. I am on an iPhone 4, 5.0.1 jailbroken. Please help.