Since firmware version, we inhibit (by default) the option to insert letters in the dial screen.

In order to restore this possibility you can turn off the setting block_url_dialing

You can perform this in three ways:

  1. Through the Web User Interface (Advanced - Behavior (Tab) - Phone Behavior (Section): Block URL Dialing)
  2. Via HTTP Request
  3. Via provisioning

Once you have turned Block url dialing to off, you can enter letters again in the dial screen:

You have to change the input keyboard from "123" to "abc", by pressing the first contextual key button: