failing to pay a insurance claim

Hi<br> My mum had a russells account which had a group life insurance. My mum got sick from october last year and due to that her account fell in arrears. Unfortunatly she passed away in december 18 2015. Been to the store with the death certificate and documents for them to close the acc down. The store then advised us to pay the arrears amount of 1200 and proceed with the claim as dey said the insurance was about 200 a month and january the account would av been freed.so if updated the insurance will pay the store and free it and also pay the balance to the benificary.so we did as we was told and there after proceeded with the claim only to be tols by the insurance comapny that the insurance lapsed in november. My argument is how can the store mislead us in paying the account and also acept payment from us which in the payment inclued the insurance premiem aswell. And not pay a claim out if they acept the payment for a insurance which they say lapsed. Hope to get sum joy from this poor customer service and someone who can advise a way foward<br>