I cannot activate my FaceTime in my iPhone 4S

Can you please post the exact error message your getting when you are trying to set this up? Are you also using a prepaid sim?

Facetime is not an app on the 4S, it is integrated in the phone app.  But Facetime is not available in certain mid-eastern countries.  What do you mean by "automatically activate" facetime - you have to manually activate it in the Phone app - find a contact and click the iPhone number, then select facetime from the options.  Be sure Facetime it "on", settings>Facetime.

I get the following message "An error occurred during activation. Try again".

The message above appear when I try to active the FaceTime from settings. The sim is monthly paid. Thanks again, Mario.

I don't get an error, or a notification. I have had to go to Settings-FaceTime to find that it says Activation Unsuccessful, turn FaceTime on and try again.

So I've turned it off and back on several times now but no luck.