Yes, you can watch Harry Potter on Netflix through your phone as long as you’re in the UK, Australia, or Japan (where the movies are licensed). Both of my top-recommended VPNs have native apps for Android and iOS, so you can safely watch these movies with no lag. Just make sure you’re connecting to a local server from a country where Harry Potter is available (e.g. a UK server if you’re in the UK) so you’re not breaking the platform’s Terms of Service.