Custom XML response after pushing message to SQS queue from API Gateway

I have implemented the x-amazon-apigateway to directly push the request to an SQS Queue from the API Gateway. I am getting the default XML response after posting a soap request using Postman. I wanted to receive a custom XML response. I am using openapi 3.0.1 yaml file for the integration. However the code to do this is not working and I am still getting the default XML response. Any idea on how to do it?

openapi: "3.0.1"
info:
    title: API
    description: "API that integrates SQS with API Gateway"
    version: "1.0"
paths:
    /:
        post:
            responses:
                default:
                    description: "Response for POST /"
            x-amazon-apigateway-integration:
                type: "aws_proxy"
                integrationSubtype: "SQS-SendMessage"
                credentials:
                    Fn::GetAtt: [APIHttpRole, Arn]
                connectionType: "INTERNET"
                payloadFormatVersion: "1.0"
                requestParameters:
                    MessageBody: "$request.body"
                    QueueUrl:
                        Ref: mySQS
                responses:
                    default:
                        statusCode: "200"
                        responseTemplate:
                            application/xml: >-
                                <Body>Sucess</Body>