You don't need to search for another phone. Just search the forums for a 10.2.1.xxxx autoloader that you were using before you upgraded to 10.3.1. Be sure to back-up all important information because an autoloader will wipe the phone clean as it installs the OS.
Then you will be back to a more stable phone running the OS you were using before. Just be sure to turn off auto updating right away so your phone won't update to 10.3.1 again.