having problems with iPhone 5s using a Verizon sim card from Straight talk. Changed from an iPhone 4 to an iPhone 5s model A1533 unlocked Verizon. I have had straight talk and love the price and the connections I have had in the past, but having problems getting this phone to work. I have verified that it was unlocked. But when the CDMA Verizon sim is in the phone and even when they activate it says network unknown and doesn't even show my phone number. Straight talk is saying that because it has been used on the Verizon network I can't switch it to the AT&T sim.? Anyone have a fix for this?