Who are Ahmadis? Do they believe that Ghulam Ahmad Qadiani is a nabi or mahdi? How can we rebut their claims about prophethood of Ghulam Ahmad?
Ahamadis and Qadianis are believers in the divine origin of the teachings of Mirza Ghulam Ahmad Qadiani (d 1908). Both the groups however, have different beliefs regarding Ghulam Ahmad's position and the position of the Muslims who rejected the claims of their religious leader. I would refer you to an article by Ahamdi's themselves about the difference in the position of both the parties: http://www.ahmadiyya.org/qadis/92-4.htm
One group believes that the said Mirza was a prophet. The other says he was the promised messiah and a mujaddid. Despite the apparent difference both the groups believe in the divine origin of the said Mirza. These beliefs are not acceptable in Islam. For our view on religious and legal position of these groups please refer to: http://understanding-islam.org/related/text.aspx?type=question&qid=296&sscatid=374