Effective communication and feedback are crucial in agile development. Extreme Programming (XP) embraces both communication and feedback as interdependent process values which are essential for projects to achieve successful results. Our research presents the empirical results from four different case studies. Three case studies had partially onsite customers and one had an onsite customer. The case studies used face-to-face communication to different extents along with email and telephone to manage customer-developer communication inside the development iterations. Our results indicate that an increased reliance on less informative communication channels results in higher defect rates. These results suggest that the selection of communication methods, to be used inside development iterations, should be a factor of considerable importance to agile organizations working with partially available customers. This paper also proposes some guidelines for selecting proper communication methods.