Actually from the old Greek manuscrips that supposed they change the name Yahwe(the correct pronouncation for Jehovah)with Lord, we find no evidence of the Watchtower's accusation regarding changing Gods name.
But since the leadership of the WT are a banch of unaducated old people, have NO idea of Greek language, The Father, Jesus, and the Holy Spirit share the same name. And there are many biblical verses that indicates this clearly to us. And the common name for them is Yahwe. Jesus said this when he asked his disciples to baptize in the Name of the Father, the Son, and the Holy Spirit. The 3 Persons of the Trinity share the same name. It is very simple.
But of course the main problem was Rutherfords attitude towards the Bible Students, the real followers of Russell, and he wanted to take the credit for him self, so he came up (after drinking a couple of bottles of Scotch)of changing the name to Jehovahs Witnesses. So actually they became Josephs Witnesses.
But he forget also that Jesus said that you are my Witnesses, and you will suffer for my name, and what ever you ask in behalf of my name I will give it to you. Also Jesus said that I'm the way and life. In Antioch the Jesus followers the use the name Christians in order to identify themselfs as followers of Jesus. So God asked for us to use the name of Jesus, so it should be Jesus Witnesses.
But Jesus also he called him, Father. And the is the correct way for a Son to call his Dad. You don't call your father by his name. And this is another problem that WT has. The Israelites they had Master - Slave, relation with God and that is why they are refering God with His name. But Christians do not have this relation with God. Christians they use the word Father for God, because they are now children of God through Jesus sacrifice.
So this makes JW's slaves and it is correct for them to use the name of Yahwe when they are calling God...