I am new to this custom shipping method. However I gone through the available documents and able to create a carrier service via API and it is showing in the checkout page with an unknown(DHS 1270..) shipping price. Can anyone help me to set the shipping price. I am not sure how the shipping price is coming in the frontend now. Also I am not sure how my call back URL file looks like. If anyone can give me a sample call back URL file for a reference it will be great. I am using PHP for the carrier service.