Recently I changed my mobile number and wanted to update it on Yahoo Messenger. I explored all the options and at last found the way to edit or remove it. If by any reason want to change or remove your number, here is a step by step tutorial to do that.
1. First sign in to Yahoo Messenger
2. At the top click on Messenger and select Privacy Options
3. In the left hand side panel, at the top, click on General
4. Now in the right hand side panel, at the bottom, click on Edit Mobile Phone or simply hit P from your keyboard
Note : If you do not have Yahoo Messenger follow this link and sign into your Yahoo account
5. After visiting Yahoo Mobile page, click on Edit at the right hand side.
6. If you want to completely remove your mobile number, clear the text box and select Change and if you to change your number, enter the new number and click on Change
7. Another way to completely remove your mobile number is to select the Delete option on the first Yahoo Mobile page