Can I block a number on this phone HTC One M8 for Windows?

I would suggest trying the call + SMS filter app available from the Windows Phone App store. It may work with the M8. Please try it and post back here with your results.
 
On my Nokia 920 if I hold down on a number when viewing call history the menu that pops out has block this number as an option. I don't know if this is a WP feature or Nokia feature but its worth a try.
 
Under settings is the call + SMS field. That is where nokias block phone numbers if my first suggestion works. I don't know why there'd be an app when its part of the os.
 

Forum statistics

Threads
342,276
Messages
2,265,354
Members
428,861
Latest member
sixsigma