Cleaning a Smartphone data can be done by you by simply going to factory reset. If you don't know to do this then you can contact your nearby communication center to do the task. Now you can present your old Smartphone (or Tablet) to someone else, like to sell it or dump it and to buy a new device. In this case you must care about those data that you had saved in that device. Not only count for those visible data but also those data, video and images that you had deleted. Now it is possible for people to recover those deleted data in Smartphone by using any of the recover software that are freely available in the internet.
So if you are planning to leave your Smartphone in another persons' hand, follow these steps before to give away.
Use your existing net work service providers' service to back up all your contacts and data.
Or use Google Dive or Cloud to store your important files.
It is very difficult to recover your data later, once you had left it with your device.
Make sure you got enough battery power to delete the data and it is better to get it plugged in to the power source as the process will take hours to clean the device.
If your device operating system is Android 5.0 or higher version,
Go to settings to Security to Screen lock
Now your device is free without any of your data and no one can recover any data from it.
To make sure, bring in new large files and make the device storage (flash memory) to be full and delete them.
Install the app iShredder to digitally "shred" the data.
Now you can feel free to give away the device.
Public holidays, Sundays and Poya days are the best time to make low priced calls to any part of the world from Sri Lanka through out the day and night.
International country code of Sri Lanka is +94 or 0094.