Why is my aussie sim data plan not working?

[AC Question]

Hello! I'm using my sprint Galaxy s5 in Australia. Sprint unlocked it as I'm able to make calls and texts while using my new Australian sim (optus network). However the data doesn't work. I've tried my sim in another phone and data/calls/text all works. I've also tried other aussie sims in my phone and only calls and texts work again. Called sprint and they're saying nothing more that they can unlock. Apn is setup correctly verified by myself, optus tech support, and optus tech support at their store.

 

[Aliesha Farrington]

There might be a frequency issue? You contacted optus tech support, what did they say?
I can only think of frequency issues (Optus uses 900ghz from memory) but I'm certain tonnes of international phones come into australia and should work. There's also the question of if the phone number is set-up properly. I know that Vodafone have different pre-paid systems, one can give you data but will only last 30 days, one gives you no data but will last a year, stuff like that. But you said you tried many different sims and still nothing.
Are you using pre pay or post pay?