All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
If what is meant is that the guardian conducted the marriage contract over the phone, then this marriage is problematic in two ways:
Firstly: conducting the marriage contract over the telephone: the Islamic Fiqh Academy issued a resolution that the contract in this case is void.
Secondly, conducting the marriage contract with the testimony of a man and two women. The testimony of a woman in the marriage contract is not valid according to the view of the majority of the jurists contrarily to the view of the Hanafi School of jurisprudence.
However, the view of the majority of the scholars is stronger. The testimony of two trustworthy male witnesses is an obligation.
Based on the above, it is obligatory to renew the contract fulfilling the conditions for a valid marriage contract, and if the guardian is unable to attend, then he may appoint a man who would conduct the marriage contract of the woman who is under his guardianship.
There is nothing wrong for the guardian to call someone by phone and entrust him to act on his behalf in the marriage contract.
There is no sin on these two spouses for their sexual relation based on their belief in the validity of the contract, and if there are any children, then they are traced back to their father because he believed that the marriage was valid.
Finally, it should be noted that one should ask the scholars about the Islamic ruling about whatever he needs to know before doing the action as Allah says (what means): {…so ask the people of the message if you do not know.} [Quran 21:7]
Allah knows best.