Call Answered on Another Device

About a month ago I received an audio facetime call on my iphone, I did not answer it because I did not recognize the number. I realized later that it had been answered on another device. Since then I have changed my apple id password and removed my apple id from being shared with my old iphone 6 that I turned into Sprint about a year ago when I got the iphone X. However, today I received another audio facetime call from the same number. It rang for about 2 seconds then stopped. Again, it has been answered by another device. I went to setting > Facetime and found that I can only be reached through facetime via my phone number not through my apple id. I am just very confused by all of this and would appreciate some answers to how this is happening.