What is the ruling on committing zina over the phone, how does one repent from that, and what is the solution to the problem of parents refusing to marry off a committed young man due to their customs?

You must repent and sever the relationship with the young man immediately, for forbidden relationships are a precursor to zina (fornication/adultery), which is prohibited. Zina is not only zina of the private parts; it also includes zina of the eye, tongue, and hand. One should not be deluded by the possibility of balancing bad deeds with good deeds, for death comes suddenly. Nor should one despair of repentance, for Allah accepts it.

As for a father preventing his daughter from marrying a suitable and religious man, this is an act of 'adhl (unjust prevention). If proven, the daughter has the right to bring the matter before a judge to have the guardianship transferred. It is advised to be gentle and affectionate towards parents, even when disagreeing with their command if it involves disobedience (to Allah). If the young man is religious and of good character, righteous people can intercede for the marriage.