Thank you very much for your telephone call offering me the position of XXX Post with the XXX Company. While I believe firmly in the work offered by your organization and appreciate the challenging opportunity you offer, I have decided not to leave my current organization which I believe more closely matches my current career goals and interests. Therefore, although it was a difficult decision, I must decline your offer. I do appreciate all the courtesy and hospitality extended to me by you and I wish you well in your endeavors.