Failed to pay funder account cash back money

I have been with Discovery car and home insurance since 2017. I cancelled my premium due to immigration. They told me to save all cashback money into funder account, I started to save money from 2020. They told me that they don't want to refund my funder account money or cashback money due to 3 years time period. They never told customers these points when we signup contracts and they always hide these tings under table. I am totally disappointed with their system. I lost all my cashback money. Please don't trust their cashback system.