He wants to get in touch with a Christian girl and marry her if she becomes Muslim
Question

                At university I got to know a Christian girl and I grew fond of her, but out of fear for my religious commitment and my future I changed universities lest I become more attached to her. Please note that I only saw her during lectures. Do you advise me to speak to her by phone so that I can tell her that I would like her to become Muslim so that I can marry her?.
Praise be to Allah.
    Firstly: 

    We praise Allaah for having blessed you with faith and 
    insight, which made you realize the seriousness of the matter from the 
    outset and take this decisive step of changing universities. We ask Allaah 
    to increase you in faith, guidance and piety. 

    What happened to you is one of the bad effects of mixing in 
    schools, workplaces and so on. Hence Islam in its wisdom forbids mixing. 

    Beware of following in the footsteps of the shaytaan, for he 
    will not try to tempt you openly, especially since he has seen your firm 
    stance, rather he will come to you in a way that appears to be good, which 
    is calling this girl to Islam and marrying her as Allaah has permitted. 

    Allaah says (interpretation of the meaning): 

    “O you who believe! Follow not the footsteps of Shaytaan 
    (Satan). And whosoever follows the footsteps of Shaytaan (Satan), then, 
    verily, he commands Al‑Fahsha’ [i.e. to commit indecency (illegal sexual 
    intercourse)], and Al‑Munkar [disbelief and polytheism (i.e. to do evil and 
    wicked deeds; and to speak or to do what is forbidden in Islam)]. And had it 
    not been for the Grace of Allaah and His Mercy on you, not one of you would 
    ever have been pure from sins. But Allaah purifies (guides to Islam) whom He 
    wills, and Allaah is All‑Hearer, All‑Knower”

    [al-Noor 24:21]

    Beware of speaking to her on the phone, for fitnah 
    (temptation) may result from listening to a person’s words as much as from 
    looking, and being in touch may make you want to see her, and thus a person 
    will get used to what he fled from, and worse. 

    If the issue is simply to tell her that you want to marry her 
    if she becomes Muslim, then this can be conveyed to her by a woman, but the 
    matter will not stop there if you get in touch with her, rather she has to 
    get to know you and get to know Islam, and find out how interested she is in 
    forming a connection with you and so on, one thing after another, and these 
    are the steps that come one after another. Then when love is established in 
    the heart, it can only be expelled with difficulty, and that has caused some 
    people to leave Islam, Allaah forbid. 

    In some societies it is rare for a woman to convert from 
    Christianity to Islam, then you will end up committing many evils in order 
    to achieve what you imagine is a good end. 

    In conclusion, we do not advise you to get in touch with her. 
    It is better for you to forget about her, unless you can find trustworthy 
    women who can call her to Islam and encourage her to marry you, without you 
    having anything to do with it at all. 

    We ask Allaah to protect us and you from all evils, trials 
    and temptations. 

    And Allaah knows best.