I can't make/receive calls or texts on my iphone 4s! How do I fix this?

I can't make/receive calls or texts on my iphone 4s! How do I fix this?

Added (1). When I got this phone, I had to unlock it to get the service to work. It has been working for a long time, but then I took out the sim. After putting it back in, there was no service and I can't call or text! I did everything the Apple website told me to, but it's still not working. Also, usually there would be the word T-Mobile at the top left corner, but now it only has the Wi-Fi bars and the reception dots.

Pay your bill

Turn airplane mode off.

If Airplane mode is on, then turn it off.
If you have no internet, make sure you are connected to Wi-Fi.
If all else fails, go to apple.

  • Why won't my new iPhone 6 (AT&T) send or receive texts/calls? I activated it two hours ago and backed it up with the data and phone number from my old iPhone 4. Both phones now read AT&T and show cellular signal and data in the top left hand corner. But when you text or call my phone number, the iPhone 4 receives it. Why won't my new phone receive it?
  • Why doesn't my iPhone send or receive calls or texts? I purchased an iPhone second hand on t-mobile, 3G works fine but can't receive any calls or texts or send them. Thought the IMEI might have been blocked. Any ideas?
  • Verizon iPhone 5c can't make or receive calls? I recently got a verizon iPhone 5c as an upgrade. I've been using it for about a week and everything was running smoothly. Then all of a sudden I can't make calls or receive calls. I can text, browse, and use iMessage perfectly but when I try to call someone it makes the "beep beep beep beep" noise you hear in horror movies when a payphone doesn't work anymore, or when a landline is busy. It's just a repetitive dialtone.
  • My iPhone 5c randomly said 'searching. ' And I can't receive any calls or texts or send them? But the network is fine with my family's phones. I've tried airplane mode, resetting my phone 3 times and taken out my sim. Please I'm desperate to get this fixed!