How can I support fAcetime in my iPhone

Read this support guide, paying particular attention to point 1

Find or restore a missing FaceTime app - Apple Support

Regards

Giulio

iPhones meant for certain Middle Eastern markets will have

FaceTime only in a few countries and only with specific

wireless providers within those countries; such iPhones

will not have and cannot install FaceTime outside the

restricted areas.

What is the model number of your iPhone? Settings>General>About>Model.

You may have to scroll to see the entry for Model.