It sounds like Siri is mis pronouncing names that used to sound just fine before iOS 7. It sounds like Siri may be using a different accent than it used to. I recommend checking the language settings for Siri to see if the correct dialect is selected.
Go to Settings > General > Siri > Language.
From: iOS: Understanding Siri and VoiceOver voices
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Joe, did you ever resolve this? I have the same exact problem teaching Siri how to pronounce the name "Wagner". I will teach it and it will say it correctly once, but every time after that, it pronounces it "Vagner" as if with a German accent. I was hoping this was fixed in iOS 8 but the problem remains.
Unfortunately, the problem remains—and is unaffected by any updates. It is incredibly frustrating to this day that my wife's first and last names (i.e. the words Siri says most often) are completely butchered by Siri. Both names are normal, and the pronunciation training hasn't worked for me at all... not on her name, nor on many other names in my contacts.