Baaki Nira comments

If you want a new phone every year or so, you can use the following method and switch the carriers regularly. You have to put in some effort then you can get a reasonable deal from Big ones. Like my current deal, I pay around 6000 for 20GB data and 5 minutes call free, I know this is little bit expensive but I got a Galaxy S9+ for free. For this I had to roam around 2-3 AU stores checking what they offered and telling the next store what the previous one offered and if they were willing to better that.

If you do not want new phones every year or so, you can use Rakuten mobile. It has better service than most. For heavy data user(50+GB per month) like me, get a pocket wifi. If this is done, you can get a Rakuten sim and pocket wifi for around 6700 per month or low. I am planning to switch to rakuten in a few months time.