Answer:
(Fatwa: 36/39=L/1429)
If you have given her only one Talaq, then you can revoke the same within iddah period. For revocation, you can say at phone to her: I am taking you back. But, if she is out of iddah (which is three menses) then you have to perform Nikah again.
Allah (Subhana Wa Ta’ala) knows Best
Darul Ifta,
Darul Uloom Deoband
