If you don't want to lose your contacts list on your phone, it is a good idea to keep a backup on your Jottacloud account.

We have made it simple to keep a your contacts list backed up, with automatic backups from your iOS or Android device.

Under the Settings menu, tap on the Contacts option.
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This will present you with the following view:

Here you will have the options to: 

Your contacts list is backed up in the VCF file format. This format can be used to restore your contacts to mobile devices or desktop computers.

Read more about restoring contacts