Iphone4 was replaced by Unicom's 3g card, but after that, you can only make and receive calls, but you can't send and receive text messages.

Unicom has regarded your information as spam. It should be that your SMS function has been blocked. After using Unicom, there are still many things to worry about in the future. Call to complain. Be kind, but firm. Tell Unicom when not to reply before. You will complain to the Ministry of Industry and Information Technology. My previous one was blocked. I kept pushing the phone and said to solve it for me within 48 hours. Is this not a joke? I complained to them. I complained for less than two hours.