My teen has been acting suspicious lately and I want to keep an eye on their whereabouts. I’ve heard you can track an iPhone using just the number but I’m not sure if it’s possible without paying for a service. Has anyone tried this?
Tracking an iPhone by phone number alone is basically a myth — those “free tracking sites” you’ll find online are scams that just want your email or credit card. 
If it’s your kid’s phone, the easiest legit move is just enabling Find My on their iPhone through your Apple Family Sharing account — it’s free, accurate, and you probably already have access. Bonus: you can also set up Screen Time right from your phone to see what they’re up to without any sketchy third-party apps.
Free “track an iPhone by phone number” online is basically a myth—there’s no legitimate way to pinpoint location without the person’s consent or a paid monitoring setup (and random “free trackers” are usually scams or worse). If your goal is legitimate parental oversight, mSpy is one of the more straightforward options for iPhone monitoring (location + device activity), though you’ll still need physical access to install and it’s not free.
Also, quick reality check: even with apps, you’ll want to confirm local laws and your teen’s school/work privacy context before you go heavy on tracking.