Triune God, modalism, or are you heretic?

[KSA]

Originally Posted by UntoHim

I strongly disagree, at least with the part that saying the Father was in Heaven can lead to a kind of tritheism.

Just WHOSE voice was THIS:
"and behold, a voice out of the heavens said, "This is My beloved Son, in whom I am well-pleased"
Matthew 3:17

Last Saturday I had a conversation with Jehovah Witnesses. What puzzled me is that they believe that God has some kind of spiritual body and is located at a special place, they call heaven. They seem to deny the omnipresence of God.

Of course, the Father was in Heaven, when Jesus was on the earth. But it does not mean that the Heaven was some kind of distant place and that the Father was located only there. The Father was in Heaven, but He was also in Jesus. So my question still stands: is it possible to separate the the Son from the Father? And did Jesus do anything the Father did not participate in?