Hey guys so my phone decided to upgrade itself to ISO 7.1.2. Its a At&t Iphone 4s and I successfully jailbreaked it using Pangu. So at first i could not get pass the SIM activation screen, as I am using t-mobile. I borrowed my friends at&t sim to get pass that and it worked, but... now when I put my t-mobile sim card in. The spring board automatically restarts and need to activate the sim again. I have attached a picture of the message I am receiving. I've also been looking on the internet for the past few days with no luck and having issues downgrading. Please if anyone knows how to get pass this I would appreciate the help. Thanks.