Knowledgebase
How to make optional the customer phone field in the admin panel of Magento
When you add/edit customers from the admin panel of your Magento you're required to provide a telephone number by default. If you want to make the phone field on the backend an optional one so that you can add customer addresses without specifying a phone number, you can do that with a single modification in the database in which your Magento is installed.
First, you need to access phpMyAdmin. You can do that from the Databases section of the Pixie control panel. There's a phpMyAdmin link in the black area on the right. In phpMyAdmin all the databases that you've created are listed in the left frame. Click on the name of the database in which Magento is installed. This will display its tables in the right frame. Find the table magento_eav_attribute; magento is just an example table prefix, in your case it will probably be a different one. Click on the name of the table. Then find the row with telephone as a value for attribute_code. There will probably be several pages with attributes so you'll have to look through them; you can change the pages with the drop-down menus above or below the table rows. When you find it click on the Edit button of that row. On the page that opens change the value for is_required from 1 to 0 and click on the Go button at the bottom of the page.
On a similar subject you may find interesting the article on removing or making optional the phone field on the checkout page in Magento and the one on removing or making optional the phone field in the customer settings on the frontend of Magento.