How to move sms from android to iphone after both are setup

I have my iphone already setup with some old text and apps. I have my android already setup with a lot of text and apps. I want to move all my texts and sms from Android to iphone without reset the iphone. How do you do that? The "Move to ios" app only works for new iphone setup. In my case my iphone is already setup and have old texts I want to keep. In fact I want to merge the text from both phones to my iphone.

I tried lots of phone transfer apps, but somehow none of them gave me an option to transfer sms after I linked the 2 phones. Apps I tried and failed include smart transfer, mobiletrans, at&t mobile transfer, copy my data, sms transfer & backup, and some others. I wasted the last 8 hours looking around and I can't find one that works. Many app doesn't even seem to have a correspond one in the other OS.

This is so unnecessarily difficult. Please help.