Wow, this is a blast from the past.
Many years ago, before most phones had mobile internet, I was running a web-to-WAP reverse proxy using https://web.archive.org/web/20080209153558/www.hottproxy.org... to get mobile web access on my LG VX 5400 flip phone.
You could go into the secret admin menu, reconfigure the WAP gateway away from the carrier's captive portal to your own proxy and voila! Unlimited free access to the real web! (at 3G speeds)