Yes that is the correct answer. Best way to avoid roaming charges is to keep your handset turned off until you comeback to the US.
Even if you turn on the handset for a few moments, and the foreign network registers missed calls or receives messages, there will be roaming charges. I hope that helps.
I am heading to China next week and this will be first visit using SGS2. In years past I used to have BBs. In those you could switch on Wi-Fi and UMA while keeping the cell tower connection switched off. In the case of SGS2, does this mean that the only way to avoid suprrise roaming call charges would be for me to use something like an iPad in Wi-Fi areas and use T-mobile App Bob Sled for calls back home, and never switch on my SGS2 to avoid a call coming through? If that is the case an SGS2 cell phone would be a downgrade for me. In that case, do you think the safest way to avoid ANY charges while overseas is to remove from my plan :
WorldClass International Service ?
That said, I have a very important question. If I have roaming not enabled on my SGS2 will I still be charged data roaming charges while overseas? The reason I ask is because even when I have my "use packet data" option switched off on my SGS2, I do see that my Onavo data monitoring App shows that Android operating device used some data!
Some tips on how to stay within your monthly cellphone usage limit in abroad.
1.Use free Wi-Fi as often as possible
2.Occasionally put the phone on airplane mode, temporarily disabling it
3.Make sure apps aren’t running in the background, using data unknowingly
4.Turn off cellular data while traveling
5.Get a local SIM card, or travel plan or international calling card from your wireless carrier to reduce roaming charges in Mexico.For this first, your phone must be 'unlocked' to work with SIM cards on other country networks. Your mobile provider may do this for free if you contact tech support. Alternatively, cell phone shops or online vendor like Unlock-Zone.com will often unlock your phone for a small fee.
6.Monitor data usage.