hello. My name is***** can help you with your question.
By default, contacts under Windows and contacts under your Apple cloud contacts and calendar are not directly compatible. The only thing you can do to correct this is either export them from one and then manually import them into the other, or you can use a software like companion link to synchronize between the 2 different platforms. What were you using previously to synchronize contacts? Were you using a Windows system? It sounds like you are trying to change more than one thing at once. I would suggest starting with one – either the changing of your Verizon to Comcast or your changing of the device and then once that is done, tackle the other.