If the Eijab and Qubool (proposal of marriage from girl to boy and his acceptance of the same) are made on phone or internet then it is not right, since in Nikah it is compulsory that the Eijab and Qubool are made (from boy and girl or from their representatives) in a meeting before two witnesses. It is also necessary for witnesses to hear this conversation:
و شرط سماع کل من العاقدین لفظ الآخر و شرط حضور شاھدین حرین مکلفین سامعین قولھما معا (الدر المختار: 4/91)
However, if they want Nikah on phone or internet (as both are at some distance) then any of the boy and girl should appoint someone as his/her wakeel (representative) for Nikah on phone or internet. Then, if the boy is present in the meeting of Nikah, the representative of the girl will do Eijab on behalf of her before witnesses in a meeting of Nikah and the boy will agree to it. And the vice versa.
Allah (Subhana Wa Ta’ala) knows Best
Darul Uloom Deoband