When your mobile can't find reception to it's own cell network, it will roam on another network's cell towers. This makes for a seamless way while calling and incurs no extra charges. 3 does this by piggybacking on Telstra's network.
With data downloading, it is a whole different story.
Normally, mobile carriers will charge you roaming rates for overseas data use. 3 however, charges even when it roams locally!!
Hence, if you're on the move and you lose 3's reception, and you're using an app which requires data usage, then you may well be incurring roaming charges! However small they may be, I'm sure none of you want to pay anymore than the amount you're already being charged monthly! With 3, roaming on Telstra's network costs' 50c/MB. Now that may not sound like much, but if left unchecked, may start to rack up significantly.
How can we avoid roaming charges? There is a solution, but it's not very robust. Here's how on an iPhone:
By default, roaming is on. So we simply have to turn it off.
Go to Settings>Carrier. You should see "Searching" and it may take a few minutes to search all the different carriers your SIM card can connect to.
Once it loads, you should see a list of Mobile Carriers. You should find you are by default, ticked on "Automatic" which pretty much means roaming. Then underneath you should see 3(3G), 3, ROAMING, and Telstra. Select 3(3G) and you're done!
Now your phone will only access the 3 network and avoid the Telstra network.
No roaming charges!!
> Constant messages saying "Network cannot be found" due to 3's spotty network coverage since it can no longer connect to Telstra (even for calling!) which are terribly distracting whilst playing games!
>If you're on a train or out and about you will get these messages quite frequently.
So in the end, you have a trade-off. Do you want to live easy and incur charges, or escape the charges and cop a bunch of needless warnings on 3's dodgy network?
I'd like to see what the roaming experience is like for iPhone users on other networks. Please tell me about it!