I have been using this iPhone since July and it was so far so good. I did not have problem calling, text-messaging and using Whatsapp. However, since yesterday there was no network connectivity and I could not use the phone or text-message (unless through wi-fi). The carrier icon in the setting mode disappeared too. (I thought that my phone had such icon before.)
Do you have any solution? Thanks.
1. I did not recall that I did anything unusual.
2. I reset my phone: <Setting <General<Reset. However, it did not work and the carrier icon did not show up.