Is a wife considered divorced after her husband utters the divorce declaration over the phone, saying: "You are divorced, and your divorce papers will reach you after you hand over the children to me"? And does her waiting period (iddah) end immediately upon childbirth? And what is the solution regarding the children if the husband insists on not sending the divorce papers?

You did well by refusing the abortion. The divorce occurred when the husband uttered the divorce pronouncement over the phone. Your waiting period (iddah) begins from that moment and ends with the delivery of the child. The custody of the children is yours. You can prove the divorce by consulting legal professionals. You are entitled to claim spousal maintenance (nafaqah) from him during your iddah period, maintenance for his children, and the right to their custody. If he wishes to have custody of his children, he has priority in that regard. If he does not wish to, you may claim child maintenance and the remuneration for their custody from him.