Your iPhone must use the same iCloud and FaceTime account.

I had the same problem (getting the "must use the same iCloud and FaceTime account"error on my MBP) after switching to a new iPhone 6. It turned out that the iMessage activation had not worked when I set the iPhone up. I went into Settings, Messages (on the iPhone) and switched iMessage off and then back on again and it fixed the problem.

Your number isn't tied to you AppleID so it can't work.

Your cellular phone number must appear in Messages and FaceTime on your mac. That is the fix.

Here's the fix:iOS and OS X: Link your phone number and Apple ID for use with FaceTime and iMessage

Bummer! here on the same boat!!!. However, while using one of the Yosemite betas I was able to receive phone calls... never was able to make calls from my computer but yes, I was able to receive them. I still think there may be a solution to this.... I tried changing my Apple ID contact number (cell) to the one I use in Ecuador, were I retired. I typed the country code and it is fine. I log out of my Facetime account in all my devices and log in back on the iPhone. The first window after I sign in shows the Apple ID phone number (the one in Ecuador) and the emails were I can be reach. when I go to Next.. the number goes back to the original I had while in the USA... Well I almost restore my phone as NEW... but not sure if that will solve the problem. I have scheduled phone call from Apple Care tomorrow morning... will see.

So in FaceTime under: "You can be reached for FaceTime at"

there is your mail only, no phone number?

Pretty sure it won't work then.

Do you even have the "iPhone Cellular Calls" option in FaceTime preferences?