My dad's insurance agent cancelled the wrong policy. What can I do?

Both my mom and dad had supplemental insurance policies with Gerber, but my dad found he could get a cheaper policy from a different company. He "cancelled" his policy as of the end of February and had minor surgery in May. The hospital where he had the surgery called and asked why two companies had paid on his claims. After many phone calls and an eternal time on HOLD, we find out the agent had cancelled my mom's policy and not my dad's! So, again, two trips out of town for me (I live 2 1/2 hours away) and numerous phone calls, we get my mom retroactively reinstated, after I paid $850 for the premiums, and the agent promises to get everything reimbursed for my dad. His idea of fixing the problem is to call my 78 year old dad and tell him to call Gerber. When my dad did call, no one from Gerber knew what he was talking about and couldn't help. I started calling the agent who was supposed to fix things to tell him that my dad couldn't fix the mistake he made and his answer is to call me and tell me to call the hospital and get my dad's money refunded. So I called and talked with a very kind lady in billing, who said she would work on the issue this morning. Then I get another phone message from the agent, who needed Gerber's number again because he lost the first one, so he could call Gerber and have them request a refund.
Question 1: Can I sue this agent for the hassle and time I have spent on this and the stress this has given my dad?
Question 2: How are we ever going to make sure Dad gets all of his money back so he can pay back the money I paid for my mom's policy? I'm on a budget, and so are my parents. We should not lose out a single penny because of this mistake.
Any advice you have would be much appreciated.