NO membership certificate

My parents was on remedi medical aid from about 1980. My dad workplace changed to discovery in 2000. My dad passed away in January. I want to take out a new medical aid for my mum now. Remedi can not give me a membership certificate for my mother. They say it is to long ago. They do not keep there records for so long. Now my mum need to pay an penalty of R380.00 extra every month. I can not believe this. I tried everything. NO LUCK at all with remedy.