Below is a sample letter (also available in pdf) that you can adjust according to your needs and send to Ban Ki-Moon either by email or regular post:
post: UN Secretary General Ban Ki-Moon, UN Headquarters, First Avenue at 46th Street, New York, NY 10017, USA
To Mr. Ban Ki-Moon, Secretary General of the United Nations:
I am writing to you regarding the situation of Sajjad Ghaderzadeh and Houtan Kian, the son and lawyer, respectively, of Sakineh Mohammadi Ashtiani – the 43-year old mother of two sentenced by the Islamic Republic of Iran to be stoned to death on charges of “adultery.”
Because of their courageous and relentless efforts to free Ms. Ashtiani from a stoning death sentence and continued wrongful imprisonment by the Islamic Republic, Sajjad and Houtan Kian have, along with two German journalists, recently been abducted by agents of the Islamic Republic. They are being held in an unknown location, and there is deep concern for their safety and well-being.
In waging their battle for the life of Sakineh Mohammadi Ashtiani, Sajjad and Houtan have done more over the course of 3 months to expose and oppose the misogynies facing women in Iran than the United Nations has done in the entire 32 year history of the Islamic Republic. Their efforts have resulted in the generation of a just demand, worldwide, to end the barbaric and anti-woman practice of stoning wherever and by whomever it is practiced – something that the United Nations itself has not accomplished on its own. In short, Sajjad Ghaderzadeh and Houtan Kian’s work in defense of Sakineh Ashtiani has moved the political position of the entire world closer to embracing the universal gender equality that is ostensible a core value of the United Nations.
As a result of their valiant challenge to one of the foundational pillars of the Islamic Republic – repression of women – Sajjad and Houtan have been arrested and now need the world to rise to their defense. It is incumbent upon you, Mr. Ban Ki-Moon, to personally stand in defense of these two and demand their release and an end to their persecution by the Islamic Republic. Sajjad Ghaderzadeh and Houtan Kian have done the work of the United Nations, and the United Nations owes it to them to advocate in their defense.
I demand that the United Nations issue a call for the immediate and unconditional release of Sajjad Ghaderzadeh, Houtan Kian, Sakineh Ashtiani, and the two unnamed German journalists, and I demand that the UN issue a resolution to end the practice of stoning worldwide.