Old Mutual Group Schemes is ripping my father off since 1997

my father has numerous policies and plans with Old Mutual Group Schemes with a set Monthly premium- as is standard. however since 1997- which is when he started that policy, they have been deducting his payments- straight from his work/payslip on a "fortnightly" bases. his total premium is just over R1000 monthly but they deduct it fortnightly. I have tried to call but they apparently never answer calls and on email they respond a month or so after each email I send and they say they never deduct premiums fortnightly even though the document which I forwarded to them- which is a document I received from a branch- is written "fortnightly". I had a similar query for my cousin in 2019 and he was refunded R15 000- so there is precedent. my Father has given me full Power of Attorney on this matter and I have sent them a copy of this but their consultant told me I do not have authority to question this matter in his last email to me.