I recently unlocked my ATT Nokia Lumia 900 and would like to use it on Walmart Family Mobile (WFM) but the phone doesn’t recognize the sim. I put a Simple Mobile sim in and it worked fine. I did however notice the simple mobile sim looks slightly different than the WFM sim. The placement of the metal portion is laid out differently on the WFM sim. I also had to cut down the WFM sim in order to make it a micro sim. I know the sim works because I tested in an unlocked Lumia 710 which happens to be a T-Mobile phone.