@Ina Jam,
Having the other driver's written agreement will most likely not keep their insurance off your back. The company has more lawyers than you do and will find someway of proving that the other driver had no right to release you from financial responsibility.
What do you mean "cancelled"? Did they drop you for some reason? If you just forgot for a day (and usually have been a really good, long-term customer) you may be able to pay what you owe and not have a lapse in coverage, i.e. your accident would be covered. This is a time where it pays to be with the same company for a while. With a auto policy, it takes seven years of paying premiums to make the company a profit.