While users await the release of next build of Windows 10 for Phone, more screenshots of the build 10072 have emerged online. The latest leaks shows-off changes in the Calling user interface as well as for the first time shows-off the Office Excel app to be precise the Excel Preview app.
Calling UI changes
Outlook Contacts app (still in Alpha)
Office Excel Preview app
Build 10072 (10.0.12555.74)
The next Windows 10 for Phone build is mostly expected this week & in the worst case scenario by next week