Your first sentence appears to be a misconception:
At sunset on the second day, a great bell began to ring. Its voice was deep and sonorous, and the long slow clanging filled Sansa with a sense of dread. The ringing went on and on, and after a while they heard other bells answering from the Great Sept of Baelor on Visenya's Hill. The sound rumbled across the city like thunder, warning of the storm to come.
"What is it?" Jeyne asked, covering her ears. "Why are they ringing the bells?"
"The king is dead." Sansa could not say how she knew it, yet she did. The slow, endless clanging filled their room, as mournful as a dirge. Had some enemy stormed the castle and murdered King Robert? Was that the meaning of the fighting they had heard?
A Game of Thrones - Sansa IV
One thing all the stories agreed on: King Robert was dead. The bells in the seven towers of the Great Sept of Baelor had tolled for a day and a night, the thunder of their grief rolling across the city in a bronze tide. They only rang the bells like that for the death of a king, a tanner's boy told Arya.
A Game of Thrones - Arya V - emphasis mine
They toll the bells for days on end for the death of the king. That does not mean it is their only use for the bells.
Far across the city, bells began to ring.
Arya glanced up, listening, wondering what the ringing meant this time.
"What's this now?" a fat man called from the pot-shop.
"The bells again, gods ha'mercy," wailed an old woman.
A red-haired whore in a wisp of painted silk pushed open a second-story window. "Is it the boy king that's died now?" she shouted down, leaning out over the street. "Ah, that's a boy for you, they never last long." As she laughed, a naked man slid his arms around her from behind, biting her neck and rubbing the heavy white breasts that hung loose beneath her shift.
"Stupid slut," the fat man shouted up. "The king's not dead, that's only summoning bells. One tower tolling. When the king dies, they ring every bell in the city."
A Game of Thrones - Arya V
Tyrion turned to the three remaining knights of the Kingsguard. "Each of you will ride escort to a herald. Command the people to return to their homes. Any man found on the streets after the last peal of the evenfall bell will be killed."
A Clash of Kings - Tyrion IX