Form to connect to API

I have a travel website that is in beta. I need to use an API to receive a quote from a travel insurance provider. I have built a form and with javascript I build the xml, which is basically var xmldata = <app> + getElementById("firstFormInput").value + </app>. Once all the form inputs are passed to xmldata, I pass this to a 2nd hidden form with only 2 inputs: xmldata and submit. I submit this 2nd form and the response from the insurance company comes back to an iframe on my website. I do get a response. But because of CORS I cannot access parse the iframe contentDocument.body. I need a developer to fix this. I'd prefer javascript or jquery, ajax as a solution, but that's not an absolute requirement. I'm on a Windows web server and PHP is also available.