Old purchased apps transfer from one phone to another old Phone

Hi

I had purchased an app in my current Iphone. I have now shifted to another IPhone (Used Model which had another Apple ID) . I have changed the apple ID in the new phone. When I browse the app, it comes as inapp purchase. I have the email stating that the app was purchased with my Apple ID only. Why it still asking for money ? How to download the app without paying the money / Can apple link my ID and automatically install the app without payment ?