Unpaid life cover by FNB

FNBMy husband took a life cover in 2018 he passed on in 2019 June. Claim was made in 2019 the response was a typed policy document where they said he did not disclose that he had chronic of which is not true .medical reports were sent to fnb from different doctors then they said period was short and they started claiming premium of R1955.54 or else policy will end so that's the notication I get since 2021