All perfect praise be to Allah, The Lord of The Worlds; and may His peace and blessings be upon our Prophet Mohammad and upon all his family and companions.
In principle, a Muslim should be true in word and deed. Allah, The Almighty, said: "O ye who believe! Fear God and be with those who are true (in word and deed)"{Attawbah/119}. The Prophet(PBUH) said: "Whoever cheats us isn`t one of us."{Muslim}.
Employing deception to eat up people`s property is among the major sins. Allah, The Almighty, says{what means}: "And do not eat up your property among yourselves for vanities, nor use it as bait for the judges, with intent that ye may eat up wrongfully and knowingly a little of (other) people’s property."{Al-Baqarah/188}.
Whatever a person takes, unrightfully, through cheating the insurance company is ill-gotten money{forbidden}, and he should give it back for the Prophet(PBUH) said: “The hand that takes is responsible for what it has taken until it returns it.”{Abu Dawud}. And Allah knows best.