How do I downgrade my iPhone 5 to 6.1.3 or 6.1. Ever sense I updated to 6.1.4 my 3G won't work and I can't send picture messages or receive them . I have a unlocked iPhone 5 from straight talk and I use there CDMA( no sim ) not GSM (which uses a SIM) my phone is not jailbroken and I have called straight talk and they don't know how to fix it . I read tutorials on how to fix it but I don't own a sim or use a sim . So can some tell me how to downgrade my phone or help me do it thanks