Hi there, pingpongz.
Does restarting your iPhone help stop it from trying to automatically reconnect to that hotspot? Restart your iPhone - Apple Support Restarting can seem like a simple step, but it could possibly help resolve this.
You'll also want to ensure your iPhone is fully updated, to see if that may help as well. You can check for an update in Settings > General > Software Update. If there is an available update, you'll want to backup before updating as seen in here: How to back up your iPhone, iPad, and iPod touch - Apple Support
This article also shows how to update with a computer if that is your preferred method: Update your iPhone, iPad, or iPod touch - Apple Support
Do you see the hotspot in Settings > Wi-Fi? If yes, does tapping that and disconnecting or forgetting it there help resolve this for you? That might help stop it from automatically connecting.
Take care.