How do I get Face Time to show my new Apple ID instead of my old one?

I changed my internet provider and therefore had to change my Apple ID - not an easy straightforward thing to do. I had to contact Apple a Support and get it straightened out. However, I cannot use FaceTime as my old Apple ID (previous email) pops up and can't get my new Apple ID (new email) to show!

WHy is this so hard and complex to do! Can anyone help?

i Can't do face time on any of my Apple devices: iPhone, iPad mini or my Mac Notebook.