You might have been suffering from a very slow internet connection, here is how you can change your 3G phone to 4G.
Steps
  •   Open your phone’s dialer and input this code ##4636## or *#*#4636#*#*
  •  After you have input this code you will immediately land into a testing screen where 4 options will be displayed
    •  Phone information
    •  Battery information
    •  Usage statistic
    •  Wifi information
  •  Click on phone information
  •   Scroll down until you see set preferred network type
  •  From the preferred network type select LTE/GSM/CDMA auto
  •  Now scroll down and click the update button and you are good now
 Your phone is now 4G capable.

     If there is an error while updating try choosing another type which has the LTE. After selecting this try and update it again till you see the one that will work for your phone

Now your internet will work faster