Isa.43:10;12 is as you say speaking to the Israelites / jews of the day and its interesting to note they never from that time on identified themselves as Jehovah`s Witnesses .
Jehovah God never rebuked them for not identifying themselves as Jehovah`s Witnesses from that time on.
When Jesus walked the earth he never rebuked Jews / Israelites for not taking up the name Jehovah`s Witnesses in accord with what was said in Isa.43:10-12 "You are my witnesses "
Simply because that was not the intent of that scripture for them to identify as such.
I`m sorry if I have gone off topic .
The christian Greek Scriptures / New Testament unequivocally testify that followers of Jesus Christ are to be witnesses of Jesus and that his Jesus name is "the name that is above every other name" 'so that in the name of Jesus every knee should bend of those in heaven and those on the earth and those under the ground "Phil.2:10 NWT printed by the WTB&TS.
Acts 11: 26b " it was first in Antioch that the disciples were by divine providence called christians "
Note : By divine providence followers / believers of Jesus were to be called Christians
Not Jehovah`s witnesses.
Their are many scriptures in the NWT of the Christian greek scriptures ? New Testament that state christians are to be witnesses of Jesus there is not one scripture according to the KI ,kingdom Interlinear of The Christian Greek Scriptures published by the WTB&TS a word for word translation of Greek into English where Christians are to be witnesses of Jehovah ,their is not one scripture that says so.