Is the marriage valid if the woman spoke on the phone with her agent or with her guardian and agent during the marriage contract, and the witnesses did not hear that? And do the Hanafis permit this?

The woman's representative in the marriage contract is her wali (guardian) or his agent, and witnessing of this agency is not required. According to the Hanafis, it is permissible for a woman to appoint someone to undertake the marriage contract on her behalf without the need for witnesses to the agency, because agency is not the marriage itself, through which intimate relations become lawful. Witnessing is specific to the marriage contract itself. Agency via telephone is valid. Later Hanafi scholars have explicitly stated the validity of agency verbally and in writing without requiring witnesses for it, and the resolution of the International Islamic Fiqh Academy affirmed the validity of agency by telephone. Based on this, the Hanafis permit a woman to appoint an agent by telephone without the witnesses hearing it in the marriage contract.