Annoying: http://flex.vodacom.co.za/err/zerod-web/p/zerod-home/#/splash404

For quite some time now I've noticed that when I access the Internet on my phone through my Vodacom router, Vodacom redirects 404 errors from some websites. ( http://flex.vodacom.co.za/err/zerod-web/p/zerod-home/#/splash404) Clicking on a broken link doesn't give me the usual '404 error' page generated by the browser (on sites that don't implement their own 404 handling) but redirects me to "Vodacom Flex" which looks like a portal/search sort of thing.

Not only is this extremely annoying, but I also find it a very dubious business practice to hijack a customer's connection (not to mention their web browsing experience) in order to shove a totally ****py portal site in their face.

I've tried to find out what Vodacom Flex is supposed to be, and I get the impression that it has something to do with options to have limited Internet access without using data (or after your data bundle has run out) but surely a 404 error shouldn't trigger that behavior...