Surat has two distribution licensees, not one. Dakshin Gujarat Vij Company Limited (DGVCL) is the state-owned licensee, a GUVNL subsidiary incorporated in 2003 with its corporate office in Surat. It covers South Gujarat, which is Surat district except part of Surat city, plus Bharuch, Narmada, Tapi, Dang, Navsari and Valsad, around 23,307 sq km. Torrent Power Limited holds a separate GERC distribution licence for part of Surat city itself, the older core inside the Torrent licence area, with a largely undergrounded network.
So the honest answer to "which discom serves Surat" is: check your bill. DGVCL runs divisions across Adajan, Rander, Piplod, Mota Varachha, Amroli, Utran, Althan, Magdalla, Limbayat and the Udhna and Sachin rural belts. Pages that flatly declare Surat a DGVCL city, or flatly a Torrent city, will send roughly half their readers to the wrong counter.
Commercial terms come from the Gujarat Electricity Regulatory Commission (GERC), not from the licensee and not from us. Under the GERC framework your system is capped against your sanctioned load, every consumer category may apply, and exported surplus is credited against the units you draw at night and through the monsoon.