Terrible customer service!

My grandmother passed away months ago and policy has paid out , however the premium was still being deducted. I have helped my father to have this money stopped and refunded to no avail. Its been over two months and call agents promise to call you back which they never do, request for paperwork is being asked every other day and constantly forwarded to someone else and nowhere closer to having his resolved at all. The same paperwork has to be sent all over the place and always something else needed again. Surely they should see all of this on their system... why should it be up to me to prove that it has been deducted. The service is appalling.