Where can get help for possible life insurance fraud?

My uncle is 84 years old he has an annuity account from an insurance company.According the contact He should get check every month,but he told me that he only received 7 checks last year.He call this company and they said that all 12 check send out but some may not cash yet and don.t want to send more.Since he is old and hard hearing and no way to fight with them.Where he can ask for help to correct this problems.He also said this happen for a while.