When using my Windows Phone 7 today to make an international call using Singtel IDD 019, I realized that the call could not get through and the operator would always report “The number you have called is incorrect”. Checking the call history showed that the prefix 019 has been replaced with “+9″ by the Windows phone for unknown reasons.
After much googling, I found a way to disable this. This is part of a feature called International Assist by whoever designs the phone. To disable it, open Settings, click on Applications on the top bar, select Phone and turn off International Assist.
I am not sure which standard defines that “01” is the same as “+” as an IDD prefix or why this feature should be on by default. In any case, it’s just another hassle when using Windows Phone 7!
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