When you marry someone you say "I agree", kabool, and you are married. You do not need to repeat this after a month for three months in front of witnesses.
Similarly, if a man intends to divorce his wife, he must make a valid statement, signed preferably, in front designated officers of the land, and then the waiting or cooling off period is observed. After this time, if the couple do not resolve their differences then they are divorced ONCE. To say a single divorce procedure involves the three 'divorces' is not according to the Quran in practice or in spirit; THE QURAN DOES NOT SAY THIS.
After a divorce if, and it is a rare if, the couple see the error of divorce they may re-marry, and if they so wish this can be repeated for three marriages but on the third divorce the woman cannot remarry this same man.
Nowhere does the Quran say a man is to stick with a decision if he says something in haste or later wants to go back on this prior to a divorce becoming official. On the contrary it says:
2:224 Let not your senseless oaths in the name of God deter you from doing good to others, from being mindful of the Divine Laws, and from making peace between people. God is Hearer, Knower.
2:225 God will not take you to task for your senseless swearing. He holds you responsible for your intentional doings. God is Forgiving, Clement. [Therefore, a marriage will not be dissolved for senseless utterances of the husband or the wife]
So any demi-god mulla who says that an UTTERANCE of divorce is a valid divorce is only a god for hellfire, AND THEY HAVE MADE A HELL FOR WOMEN OVER THIS ISSUE FOR CENTURIES!
As the good Dr Saab has written, hallalah is HARAAMAH.