I have 2 iPhones, an iPhone 5 on the Verizon network, and an iPhone 4S (from Verizon) no longer on the network. The 4S has an unlocked SIM card slot. I would like to use the 4S overseas (in China) with a foreign SIM card (China Mobile). Apple and the company providing the SIM card (Telestial) both say it's possible, while Verizon says it's not. Does my 4S have to be connected to the Verizon network in order to use it with a SIM card overseas, as Verizon claims? Has anyone used a Verizon iPhone 4S abroad with a foreign SIM card? I cannot take my iPhone 5, so that is not an option. Any assistance would be appreciated. Thanks!