I am not really sure but you can try these steps from which i think you can change the language.
1. Navigate to Settings -> General -> International
2. Select Voice Control
3. Select the language you would like to use
Chinese (Cantonese)
Chinese (China)
Chinese (Taiwan)
Dutch
English (UK)
English (US)
Finnish
French (Canada)
French (France)
German
Italian
Japanese
Korean
Norwegian
Polish
Portuguese (Brazil)
Portuguese (Portugal)
Russian
Spanish (Mexico)
Spanish (Spain)
Swedish
