If you have proof you bought it, not your ex, this sounds more like a matter for the police or small claims court. The key word here is "conversion" - the legal definition for assuming control of property which doesn't belong to you. It's akin to theft.
Try the police first (bring proof that you purchased the TV, not your ex). If they won't help because the property value is not large enough, you may have to resort to small claims court. There's a small filing fee, but it will force your ex to either respond to the court order (in which case you should win if you have proof the TV is yours), or you will win a default judgment if the ex ignores the court summons. In either case, the court judgment should be enough to get a police escort to your ex's house to reclaim your TV.
If possible, I'd take steps to ward off the possibility of your ex smashing the TV and claiming it was already broken when you split. If you can somehow shoot dated video showing that the TV is working, that would be good evidence, and put your ex on the hook for the cost of replacing TV if they decide to smash it to spite you.
LOL. Control it to do what? command it to "get off from the wall and leave that $%^@ house?" They haven't and unlikely to implement a destruct function for TVs, although judging by the number of no-remote posts one gotta wonder.
There are iphone apps to control Samsung TVs https/en.softonic.com/solutions/what-are-the-best-samsung-remote-apps-for-iphone-or-ipad
but your phone and the TV have to be on the same wifi network. Has your ex changed the network name and password? If not then you might be able to screw with the TV if you are close enough to get on her wifi. I don't know if it's legal for you to do that though. Might depend on the responding officers' attitude if your ex calls them.
I don't think you can do it over the internet unless you hack into her connection.