refuses to pay out

My mother passed away of cancer and when she fell ill we claimed for severe illness which she had on her policy and they refused to pay out. Then when she passed on we claimed for her life insurance and they refused to pay saying that she **** about her other illnesses ie diabetic fyi my mother hadn't matriculated and the old out mutual advisor had completed the forms ticking everything negative and just letting my mom sign... she done blood tests before the policy had initiated and all the results were okay. Now when it's time to pay out they refuse..but to take your 1st premium they very quick. I am very disappointed as my mother wasn't well off and to have left her kids a little something was a big thing to be proud of as that sacrifice every month for her was a lot.