To cross out something in a cell in Excel, you can use the "strikethrough" feature. This will put a line through the text, but still keep it visible. Here's how to do it:

1. Select the cell(s) that you want to cross out.
2. Right-click on the selected cell(s) and choose "Format Cells" from the menu.
3. In the "Format Cells" dialog box, click on the "Font" tab.
4. Check the box next to "Strikethrough" under "Effects".
5. Click "OK" to apply the formatting.

Now the text in the selected cell(s) will have a line through it, but still be visible. You can use this feature to cross out phone numbers or any other text in your spreadsheet.