If you absolutely feel the need to change your PIN, this can be achieved by unregistering from your account and then log in again with a fresh start. Your account, together with all your access, will remain intact when you unregister.
Unregister by going to "More" and then click on "Settings" where you'll find "Unregister".

NOTE: when you unregister and then need to log in again, you MUST be able to provide your recovery code.

If you previously haven't saved your recovery code, you'll find it under "More" and then "Recovery code".
A warning notice with information will show, again notifying you that your recovery code is needed to be able to log in and regain your existing access. Click "Yes" if you are sure you want to go ahead.
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You'll now be presented with the very first start-up screen. From there you can select that you already have an account. You'll then be prompted for your mobile phone number, recovery code followed by having to input a (new) PIN-code.
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