I’ve removed your other threads. Keeping the discussion to one thread only is more likely to provide a solution.
Before we can help, please answer a few questions:
Is this an “old” (you’ve already used it before this problem arose) or a new SIM card? Did you purchase the iPhone from someone else, or is it in your possession since quite some time ago? What did you try before posting on this forum, in order to get it working again?
Try removing the SIM card and inserting it again. That might help. Otherwise, please give a more detailed description of your issue.