How can one stop a forbidden relationship that involves the release of desires via mobile phone with a young man who intends to propose, and how can he be informed of the unlawfulness of this act?

What is known as a love relationship between young men and women is not sanctioned by Islamic law; because it is a gateway to temptation and corruption. If a man and a woman fall in love, marriage is the ideal path, as the Messenger of Allah, peace and blessings be upon him, said: "We have not seen for two who love one another anything like marriage." If marriage is not possible for them, then they must turn away from this attachment. Each of them should preserve their chastity through marriage and occupy their time with what benefits them. The sinful relationship must be severed, and repentance to Allah is required by abandoning the sin, regretting it, and resolving not to return to it, while maintaining discretion and not publicizing it. One must not surrender to the whispers of Satan.