Ineed a manual for a doro 6520 - Doro Lands Phones

Question edited for clarity 'Doro', not 'door'. :>D

Press the Volume UP button when you are IN a Call. You can only do it when you are in a call. The top Plus + button on the right side. Figure 18 in the diagram.

They make these phones for the elderly, but they are really hard to use and a relic from the 1980s!!

Owner Manual and diagram
https://www.doro.com/globalassets/inriver/resources/qsg_doro_6520_en_a3a7_v362031204120512061207120812091_20190924.pdf

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https://www.hearingdirect.com/media/wysiwyg/Doro_6520_User_Guide.pdf



https://www.hearingdirect.com/media/wysiwyg/Doro_6520_User_Guide.pdf

I believe it indicates a loose memory card, but I didn't see it in the manual.

Free manual from the manufacturer's web site:

https://www.doro.co.uk/doro-6520.html

Start by going to “Contacts” and tap on the contact you want to block. Then, press the menu key at the top left of your Doro 6520. You will see a menu where you will select “Block Number” or “Add to Auto Reject List”. The title may vary depending on the model you own

This site seems to address the problem:

http://deviceguides.vodafone.ie/web/doro-6520-proprietary-os/explore-your-phone/internet/set-up-your-phone-for-internet

Follow the instructions on the screen to set up your phone and prepare it for use.

1. Find "Reset all" Press the Navigation key. Select Settings. Select Security. ...
2. Restore factory default settings. Key in the phone lock code (default is 1234) and press the Navigation key. Press the Navigation key to confirm.

Doro 6520 - Restore factory default settings - Device Guides

https://userguide.vodafone.co.nz/doro/6520...os/basic.../restore-factory-default-settings/.
or go to this link might help.
How to reset clock on 6520 mobile Google Search

6520 reset network

Unfortunately sir doro 6520 don't have this feature...