Answer:
If you're doing an interview via phone I wouldn't suppose you would need to get dressed into anything specific. If it's going to be a video call, then you should at least wear something presentable that the camera will see (that means you don't have to wear pants).
Sorry, if you're looking for some specific answer then I can't help you. This question just kinda throws common sense out there and it's just your job to use it.
Hope this helped ;)