What did ST do when her usage went beyond 100MB?
Did you end up having to pay extra$, or did the data connection just stopped? Or did you discover the high usage in time?
I'm wondering how best to control this 100MB quota for those non-tech users.
Postpaid plan will always charge you excess data at $10 for each 1GB block (regardless of your actual excess - can be just a few KB or MB, to telco still 1GB). Your monthly bill will reflect it, and you can also see your usage in My Singtel app (install it from the app store/play store).
Prepaid plan will start eating into your main balance VERY VERY FAST. Once all the main balance eaten (7-15 cents per 10 KB block can easily finish $10 top up with just around
1MB), the data service stops and you will be SHOCKED to find out main balance is zero.
ALWAYS keep an active data plan.
FYI, WhatsApp has an option to disable downloading pictures and other media when on data connection. Not sure if Android-only or iOS version has the same option.