correct of error on I-797, please help. Thanks.

There was an error of my citizenship on H4 approval notice (I-94 part). I faxed the correction request to California Service Center in last August. Now 7 months has passed, and I haven't heard from them yet. I called their customer service today, and it seemed they don't know anything. Should I book an appointment with our local immigration office and ask them to correct it? Or should I write to California center again? Can anybody having this experience give me some suggestions? Many many thanks.