Hello! Im having problems about my Iphone showing NO SERVICE on top. Im not able to send and receive msg, same with calls

Question

Hello Guys! I hope someone could help me, Im having trouble with my phone's signal, I am not able to send and receive msgs, same as make calls and receive calls. At first, my phone is working fine (iphone 4, iOS 7.0.4) and all of a sudden, my text messages are not getting through, and I noticed that my phone shows NO SERVICE, I refreshed the phone by turning it off and turning it on after a couple of minutes, it worked. My phone is okay again after that, Im able to send and receive messages again. But after few hours, the problem came again. NO SERVICE sign is displayed again, but this time after refreshing the phone nothing good happened. I tried almost every possible thing I can to fix it but it doesn't work. What should I do.
Thank you

Answer 1

Hey Clara,
These are the recommended troubleshooting steps to resolve No Service issues on iPhone:
Toggle airplane mode: Tap Settings > Enable Airplane Mode, wait five seconds, then turn off airplane mode.
Turn iPhone off and then on again.
Remove the SIM card and verify that it's a valid, carrier-manufactured SIM. Also verify that it isn't damaged, worn, or modified. Then reinsert it.
Check for a carrier-settings update. Connect to a Wi-Fi network. Then tap Settings > General > About. If an update is available, iOS will ask you if you want to install it. If Wi-Fi isn't available, connect your device to iTunes.
Update your iPhone to the latest version of iOS.
Reset network settings by tapping Settings > General > Reset > Reset Network Settings. This will reset all network settings, including Bluetooth pairing records, Wi-Fi passwords, VPN, and APN settings.
Restore the iPhone.
If you are outside the United States, please also follow these steps:
Go to Settings > Carrier > Automatic.
If the phone registers any carrier network, Settings > Carrier will be present.
If the Carrier option is missing in Settings and you are outside of the Unites States, please contact Apple for support and service options.
Set the option for Automatic to off.
A list of potentially available carriers appears after about two minutes. If the device is locked to a carrier, it may connect only to the carrier network to which it is locked. If the device displays carrier networks, then the device is working as expected.
Set Settings > Carrier > Automatic back to on.
If you're still experiencing No Service issues, contact your carrier to check for any network or account issues that could cause these symptoms.
from: iPhone: Troubleshooting No Service
http://support.apple.com/kb/TS4429
Welcome to Apple Support Communities!
Take care,
Delgadoh