The SIM card installed in Vietnam has 4 bars of signal. When I arrived in China, I couldn't use it. When I got to the airport, there was no network, I couldn't text the person picking me up. I was helpless. Luckily, a staff member at the airport lent me a phone to call the person picking me up. Overall, it was frustrating. I prepared a SIM card but when I arrived in China, I couldn't use it.