I am looking at buying a used Droid DNA and using it on my existing straight talk plan. Can anyone give me step by step directions on doing this. If I enter the IMEI number on the phone, it says it is not compatible, but I know many people use the DNA on straight talk. I just need help getting it activated. Can I just buy and new AT&T SIM and put it in? How does all of this work? I am really at a loss since I know nothing about phone set up. Thanks!