How to backup contacts, calendar and tasks from Microsoft Lumia 640 XL Dual SIM
We used PhoneCopy.com service for this guideline. Using it, your can backup your contacts from your Microsoft Lumia 640 XL Dual SIM easily. The whole backup, including the settings, can be done in several 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 can easily edit your contacts and other resources online in your PhoneCopy profile. You have access to your contact even if you forget your phone at home.
Some additional tips:
Contacts can be then transferred to another device (eq. iPhone, Nokia, SonyEricsson, Samsung, LG etc). See PhoneCopy site for supported devices.