As users continue to delete their Facebook accounts in the wake of the Cambridge Analytica scandal, a number are discovering that the social network holds far more data about them than they expected, including complete logs of incoming and outgoing calls and SMS messages.

The #deletefacebook movement took off after the revelations that Facebook had shared with a Cambridge psychologist the personal information of 50 million users, without their explicit consent, which later ended up in the hands of the election consultancy Cambridge Analytica.

Facebook makes it hard for users to delete their accounts, instead pushing them towards “deactivation”, which leaves all personal data on the company’s servers. When users ask to permanently delete their accounts, the company suggests: “You may want to download a copy of your info from Facebook.” It is this data dump that reveals the extent of Facebook’s data harvesting – surprising even for a company known to gather huge quantities of personal information.

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One user, Dylan McKay, reported that for the period October 2016 to July 2017 his logs contained “the metadata of every cellular call I’ve ever made, including time and duration” and “metadata about every text message I’ve ever received or sent”.

Many other users reported unease at the data they had discovered being logged, including the contacts in their address books, their calendars, and their friends’ birthdays.

Mat Johnson (@mat_johnson) Oh wow my deleted Facebook Zip file contains info on every single phone cellphone call and text I made for about a year- cool totally not creepy.

Ben Wigham (@bmdwigham) I had a similar issue with mine on Android. Don't have FB installed but I do use Messenger and Instagram. Interestingly they only tracked when I rang my parents and girlfriend. Have never used Messenger in regards to my parents. Weird.

Emma Kennedy (@EmmaKennedy) I’ve just looked at the data files I requested from Facebook and they had every single phone number in my contacts. They had every single social event I went to, a list of all my friends (and their birthdays) and a list of every text I’ve sent.

In a statement, a Facebook spokesperson explained why contacts were uploaded. “The most important part of apps and services that help you make connections is to make it easy to find the people you want to connect with. So, the first time you sign in on your phone to a messaging or social app, it’s a widely used practice to begin by uploading your phone contacts,” it said

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“Contact uploading is optional. People are expressly asked if they want to give permission to upload their contacts from their phone – it’s explained right there in the apps when you get started. People can delete previously uploaded information at any time and can find all the information available to them in their account and activity log from our Download Your Information tool.”

Facebook asks users for permission to upload this sort of personal data for a number of reasons: address books, for instance, are uploaded with the understanding that it will help users find friends on the social network and help the app’s algorithms work out how to prioritise different content. Messenger for Android asks for permissions to read call and SMS logs for a similar purpose.

The company notes that users can stop continuously uploading contacts and delete all their previously uploaded contacts by turning off the continuous uploading setting in the Messenger app.

Permanently deleting a Facebook account will also result in contacts no longer being uploaded and all previously uploaded contacts being deleted.