ChatGPT API: "You exceeded your current quota, please check your plan and billing details."

Question

I tried to use ChatAPI API in flutter App.

And This is the code that I use.

Future<String?> getChatGPTResponse(String prompt) async {
  const apiKey = "~~~~~~~~~";
  const apiUrl = "https://api.openai.com/v1/completions";
  final headers = {
    'Content-Type': 'application/json',
    'Authorization': 'Bearer $apiKey'
  };

  final body = jsonEncode(
    {
      "model": "text-davinci-003",
      'prompt': prompt,
      'max_tokens': 1000, // Adjust as needed
    },
  );

  try {
    final response = await http.post(
      Uri.parse(apiUrl),
      headers: headers,
      body: body,
    );
    if (response.statusCode == 200) {
      final jsonResponse = jsonDecode(response.body);
      final result = jsonResponse['choices'][0]['text'];

      return result;
    } else {
      const result = "오류가 발생했습니다.";
      print(
        'Failed to call ChatGPT API: ${response.statusCode} ${response.body}',
      );
      return result;
    }
  } catch (e) {
    const result = "오류가 발생했습니다.";

    print("Error calling ChatGPT API: $e");
    return result;
  }
}

But I keep facing below error message.

I/flutter (16756): Failed to call ChatGPT API: 429 {
I/flutter (16756):     "error": {
I/flutter (16756):         "message": "You exceeded your current quota, please check your plan and billing details.",
I/flutter (16756):         "type": "insufficient_quota",
I/flutter (16756):         "param": null,
I/flutter (16756):         "code": "insufficient_quota"
I/flutter (16756):     }
I/flutter (16756): }

I register credit card and now I'm Pay as you go . And I haven't used any API service so far.

After registering my billing info, I deleted old API key and generate new key either.

But still I have this problem.

But why do I keep facing this insufficient_quota error?