Islam is a religion of chastity and morality. It aims at building a solid society on bases of purity, modesty, morals, and good manners. By the same token, Islam blocks all ways that lead to evil to the extent that Muslim jurists adopt a juristic principle that reads: What is conductive to haram (unlawful) is itself haram.

As far as the issue of “cyber sex or phone sex” is concerned, Dr. Muzammil H. Siddiqi, President of the Fiqh Council of North America, states: “Zina according to Shari`ah is any illicit sexual intercourse. Thus pre-marital sex, extra marital sex and homosexuality are all considered Zina according to Islamic law. Zina is a major sin (Kabirah); It is absolutely forbidden.
Islam does not only forbid illicit sexual intercourse, but also forbids anything that leads to this sin and crime. ‘Cyber sex’, ‘phone sex’, etc. are those activities that can lead to Zina. The Prophet (peace and blessings be upon him) said: ‘The eyes commit Zina, the hands commit Zina and feet commit Zina and the genitals commit Zina.’ (Musnad Ahmad, Hadith no. 4258) In another version, he is reported to have said that ‘the genitals confirm or deny it.’ (indicating that starring at opposite sex in a lustful way has a spontaneous effect on the genitals and may induce person to commit Zina)

Thus, Muslims should avoid any avenue of Zina. Allah, Most High, says, ‘Do not even come close to Zina. It is a shameful deed and an evil way.’ (Al-Isra’: 32) So Allah, in the Qur’an, not only prohibits Zina, but He also prohibits even coming close to it.
With the above in mind, we’d like to clarify that really, one of the most tragic and consequential sins in which man engages is adultery or what leads to it. This heinous crime destroys families, lives and destroys within some people the hope of attaining Allah’s pleasure. But in Islam, the door of repentance is always open, only that the repentance itself demands a resolve to cease from a sinful activity. A person who has engaged himself/herself in an adulterous relationship must resolve to cease from the sinful sexual activity and return to Allah, seeking His forgiveness. Allah will surely turn unto him/her and shower him/her with His mercy.
This indicates that, sister, one should never lose hope of gaining Allah’s mercy. Rush to Allah and beseech Him for forgiveness. Allah says in the Qur’an: “Say: ‘O my Servants who have transgressed against their souls! Despair not of the Mercy of Allah: for Allah forgives all sins: for He is Oft-Forgiving, Most Merciful.'” (Az-Zumar: 53) “Allah accepts the repentance of those who do evil in ignorance and repent soon afterwards; to them will Allah turn in mercy: For Allah is full of knowledge and wisdom.” (An-Nisa’: 17)