Many Android Mobile Phone users have reportedly experienced “Mobile Network Not Available” error message when they try and attempt to make calls. Your mobile network in US, could be Verizon, T-Mobile etc. Regardless of who the network operator is, the methodology involved running in the background is same. In General, when you insert a sim and power on your phone, it establishes connection with the network, using the signals spread over by BTS (Base Transmitter Station) which you have may have seen quite a few times.
In some remote areas, there is a poor reception, and sometimes the signals do not reach the phone; this is because the BTS footprint is low or none in that area, as soon as you are in an area where the signals are strong, transmitter is nearby; the signals strength increases. The reason for this explanation is to give you an idea, that if there is no coverage, no matter what you do; “mobile network will be unavailable”.
BUT if there is a signal, it should automatically strengthen it. Sometimes, it doesn’t and here are a few methods that can help re-establish signals.
image source: wikipedia.org
Method 1: Power Cycling Process
Power Cycling can reset all the connections to the network provider, and re-establishes them with the mobile network provider. If there is a temporary glitch, Power Cycling will fix it. To do this, Power OFF your Device, remove the battery and sim card (Do it firmly and not damage the PINS). If your mobile doesn’t have a removable battery, then simply power it off for 5 minutes].
Method 2: Check Network Operators / Enable/Disable Airplane Mode
There is a setting in all phones, Android or any other to automatically pick the network coded in the SIM. If you’re mobile phone has Verizon sim in it, it will automatically pick verizon network, and vice-versa. BUT since the purpose of this guide is to troubleshoot this error; you can give it a try to manually select your network.
Typical steps to do this would be to go to Settings -> Mobile Networks -> Network Operators -> Search Networks and tapping/choosing the desired Network. If this doesn’t fixes the issue, try switching Airplane Mode on and off from settings, this pushes it as well to re-establish connection with the network/nearest BTS Tower.