If you can wait until maybe the end of September, Sony Xperia M C2004 model would have those features you are looking for. However it is an Android, not a Windows Mobile/Windows Phone.
Also, if your area is refarmed to 1900, then there are 850/1900/2100 dual-sim Android phones that would work as well, such as Sony Xperia E dual and Samsung Galaxy Grand, both North American versions.
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