Can't change anything

On 14 February 2016 my father past away. I went to his insurance broker and explained the situation. The insurance was on my dad's name. I had a death certificate. I was emailed by quickfire. I can't change anything on the policy with out letter of authorisation, can't cancel policy without letter of authorisation but apparently the banking details can be changed to my banking details with out the letter of authorisation, also with out informing me that my banking details are now being used. Resulting in me having to sit 2 hours in a bank to reverse it and getting bank charges for a debit order that should have gone off being declined due to insufficient funds. I will never do business with your firm. Also I cancelled my insurance by qiicksure about 2 years ago as your premiums and excesses are too high