How to backup contacts, calendar and tasks from Microsoft Lumia 640 DUAL SIM
PhoneCopy.com is a web service which is free for personal purposes (with few limitations). This tutorial will show you how to backup your data from Microsoft Lumia 640 DUAL SIM. The whole process can be completed in few minutes.
Download the PhoneCopy application from windowsphone.com. If you do not have a PhoneCopy account yet, press "Register new account" and create it by filling in "Registration" and then press "Sign up".
If you already have a PhoneCopy account, fill in your username and password. To export your contacts, press "Export to PhoneCopy.com". If you want to upload your merged contacts back to the same Windows Phone 8.1, it is necessary to delete all contacts there first.
Now you have all your contacts backed up on PhoneCopy and you can edit all your contacts in your online account. If you lose your phone or the stored data, or if you just run out of battery, you can see your contacts online.
Some additional tips:
Contacts can be then transferred to another device (eq. iPhone, other Nokia, SonyEricsson, Samsung, LG etc). You can always edit your contacts in your online account. Also, you will see full history of your contacts, as well as the data that you have deleted between two synchronizations.