As already stated Isiah 43 doesn't prove Jehovah's Witnesses are the true religion. The Watchtower printing corporation uses that scripture out of context as proof they are the true religion, as shown by a quick reading of the context surrounding the verse used it becomes very clear.
The Watchtower corporation scriptural exegesis is extremely self serving even more so than other religions, they take everything literally(when it suits them), and with extreme bias that they alone know what the bible "really" says and all the other religions have Satan controlling them and they alone are the true religion. It is wishful thinking that inspires their scriptural exegeses, which has caused them to print many dates for the end of the world to come and make the Governing Body rule with Jesus. They are also in very strong denial and will violently Disfellowship any member who tries to show them where they are wrong, no one of Jehovah's Witnesses can question their claims and not get DF'd.