Be sure that your webRTC is disabled on your mobile browser.

At first, go to https://ipleak.net/ to check out whether your IP is leaking even though you are connected to VPN, if you see there your real IP, then your IP is leaking.

It is easy to solve this problem on desktop browsers, check out the bottom of that page and you'll see there how to solve it.

I am using Brave Browser (based on Chromium) and Firefox. You can disable webRTC leaking on mobile Firefox just simply following said instructions, on Brave, you cannot do it. Your IP will continue leaking despite the fact you have https everywhere, adblocking etc etc.

As a person who uses VPN 7/24 I thought I needed to share this little tip, if my browser leaks my IP then why I am using a VPN anyway? I know, Firefox is laggy and slow on mobile devices however if your privacy comes first, you should bear this in mind.