Why my android device can't connect to 3G/4G

It's 4G time now! People are now exploring the pace of 4G connection. Service providers are in a hurry to get the maximum number of customers.

But due to different reasons some users are unable to connect to 4G services, or even 3G especially in Android devices.

Here's the solution to get rid of such problems.

Step 1

Check whether your preferred data connection is 4G (LTE). You can check the same by,

Setting -->  Wireless & Networks --> More --> Mobile Networks --> Preferres Network Type 

(Most probably it will be selected as 4G by default)
If you still facing issuues while connecting follow to step 2.

Step 2 

  2.1 Dial *#*#4636#*#* from the dialer
  2.2 Testing window will open. Then select Phone Info.
  2.3 Set preferred network type as required.