Typically I use my phone when not at home since at home I have a computer to browse the web of course. Is pihole installed on your iphone? Does it work when in a train, in a restaurant somewhere, etc...?
You can use pihole over a vpn.
One common example is setting up Tailscale on Pihole and your phone and then you can set the dns on whatever Wifi you’re on to the Piholes private IP