character set for xml script

Hi every one
i am working with cisco ipPhone that can get some xml code and execute them. it is like a cell phone. however this is my code :

<? 
 header("Content-type: text/xml"); 
 header("charset: UTF-8"); 
 header("Connection: close"); 
 header("Expires: -1"); 

 print("<CiscoIPPhoneDirectory>\n"); //cisco ipp tag
 print("\t<Title>Lunch Time Essentials</Title>\n"); 
 print("\t<Prompt>Who will deliver food today?</Prompt>\n"); 
 // .... other codes
print("</CiscoIPPhoneDirectory>\n"); 
?>

PHP:

but i need to display menu and content in
farsi language(not english) and
when i change content of <title> and <prompt>
into farsi, the phone shows the whole of xml code(tags)
and replace farsi content with ??? .
what do you suggest ?
NOTE : because you don't have cisco ipPhone your system can't compile
content of ciscoIPPhoneDirectory tags.
thank you in advance