Holding an old woman hostage over a certificate

GEMS are holding my mother's medical aid certificate hostage for almost a decade. When my father passed a request was sent in writing in 2015 with a letter of executorship to them. Over the last 8 years I have struggled to get feedback with each operator giving me different excuses. The last time I called, I was asked to have my mother present. When I called with her present, the operator said there is no letter on file. We are paying a higher price for medical aid because of not having proof of membership for the last 5 years. How can an organisation like GEMS be so ************ and heartless? All I want is a certificate that we have requested over the last decade for a membership that was terminated 2 decades ago.