picture problem

hello everyone i bought my wife a iphone 3g with the version 3.1.2 (7d11) for tmobile.everything is running good the only problem that im having is that she cant receive pictures. she gets a message that says(No Subject. The media content was not included due to a picture resolution or message size restriction.) im sending test pictures with my phone and no mater what resolution i put on my phone is that same problems. ive had 3 iphones prior to this one and all of them were able to receives pics and videos. plz if anyone can plz help me it would be greatly appriciated. i've been trying to fix this for the past month..

thanks