1. Switch off your phone and switch it on back.

2. It will select a network automatically. If NOT, follow the below steps to select a network manually.

Apple iOS steps to follow:

Touch Settings

Touch Carrier

Touch the slider to turn automatic network selection off

Wait while the iPhone searches for networks

The available networks will be listed

Select the network you want to use

Android steps to follow:

Touch Apps

Scroll to and touch settings

Touch More settings

Scroll to and touch Mobile networks

Touch Network operators

Wait while the phone searches for available networks

The available networks will be listed

Select the network you want to use