i cannot send sms or mms messages from my iphone to another iphone in australia from the usa

I changed my australian sim card to a usa sim in my iphone and I cannot send any text messages via sms to any other contact in australia . I have turned the sms/mms on and off and the facetime on and off and the off and on . I keep getting a message that states that i cannot send any mms text messages but I cannot do anything more via the system preferences as it does not distinguish between sms and mms separately .