Editing and scaling problem with iPhone caller ID pics

I'm having a problem with the caller ID photo function on my iPhone 5. When I select an image from my photo library to use as a caller ID picture I am navigated to a screen that prompts me to "move and scale" the photo within a circular frame to my desired specifications. If, for example, I want to select a picture of my wife, I will choose a photo and crop it so that her head and shoulders should appear properly when she calls. After I complete this step, the phone shows the picture inside the little circle in my contacts list. Then, almost immediately, the phone will automatically increase the size of the picture within the circle and the scale of the picture is no longer the way I set it. If she calls her picture is blown up, her shoulders and forehead cropped out. No matter how many times I try to correct and resize the picture the way I want it, the phone will automatically revert back to this enlarged image. I would like to know if there is a fix for this. When I "move and scale" a picture, I expect it to stay scaled. Why would the iPhone insist on almost doubling the size of the image after it has already been set? Any input on this problem would be appreciated.