You spot tooth marks on a charging cable. A live cord can cause a shock, burns in the mouth, or a fire. If your dog is in contact with live wiring, do not touch the dog or cable until power is disconnected safely. Turn off power at a safe point, get people away from the hazard, and call emergency help as appropriate. If your dog has chewed a live cord, seek veterinary care immediately even if they seem well, breathing problems and heart rhythm changes can develop after an electrical injury. Do not put fingers into an injured dog's mouth.
Once the immediate danger is over, remove damaged cords from service. Use secure cord covers, route wiring behind furniture out of reach, and keep your dog out of rooms where cables cannot be protected. Unplugging a device does not make loose wire pieces safe to swallow. If you suspect ingestion, ask your veterinarian for advice.
Work on the chewing pattern
Dogs may chew to explore, ease frustration, or meet a need for activity. Offer safe, suitable chews and supervised enrichment away from the cables. Reward choosing those items. Practice "leave it" with harmless objects, not a plugged-in charger. Notice whether chewing happens only when your dog is left alone or whether they seek out all kinds of non-food material, share that pattern with your veterinarian.
No training cue should be the only barrier between a dog and live electricity. Make the physical environment safe first.
Sources: Dogs Trust: Destructive behaviour in dogs - how to stop it. MSPCA-Angell: Electrical Cord Injury.