Why Jehovah witnesses only call God with the name Yahweh?

I'm Christian. The bible clearly don't write the name of God as 'Yahweh', but 'YHWH'. And also our God have another name, Jesus Christ. Why Jehovah witnesses seems like to call God 'Yahweh' instead of Jesus??
Update: @PeterPan i dont know what you are talking about, this is the first time i asked this.
Update 2: so, to all JW out there, do you ever call God in your prayers with the name Jesus??
Update 3: i see.. si JW don't believe in holy Trinity?? is that full of deception? Jesus says "I'm the only way"
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