Cancellation of membership from South African Police Union (SAPU)

I was employed by South African Police Service for years under South African Police Union(known as SAPU). Last year August I resigned then went to work for a private company for 1 month, then again went back to government but different department on October. What Ive noticed in my payslip is that SAPU is still deducting money on my payslip til to date and I tried to engage with them via calls and emails to let them know that Im no longer at police force, they must cancel my policy. Since here we are represented by different union. Till up to date I have not received any correspondence from them… they are still deducting from my payslip. Right now Im paying two unions each and every month. Kindly assist me on escalating the matter HelloPeter. I need your help on cancellation of SAPU