Very questionable work ethics

My elder mother has been having a policy with b3 for many years. 10 sept 2015 they claimed she did not pay and was in arrears, I had to scan & send proof. This week again they are stressing her saying she owes for two months and now she must send proof from January 2017 until November 2017. Seemingly if one could die, they can refuse to pay claiming we owe. This is no way to treat elderly clients.