WCF Restful Https for a single method

I have a RESTful WCF that I'm using for a mobile application, I need a single method, the payment method, to use HTTPS, I do not want to enable HTTPS for the whole service because some methods return a large amount of data and it would be too heavy for a cell phone. It is possible? how?

I would like to know if you have any ownership or other way of allowing this method to be accessed only when using a secure connection ... Something like ...

[OperationContract]
[ExigirHTTPS(true)]
[WebInvoke(Method = "POST", UriTemplate = "/Disponibilidade", RequestFormat =     WebMessageFormat.Json, ResponseFormat = WebMessageFormat.Json)]
DisponibilidadeRS Disponibilidade(DisponibilidadeRQ request);