Since last year November I've been having a problem with FNB life claiming that my account does not have enough funds when they have to deduct monthly premiums

Since last year November I've been having a problem with FNB life claiming that my account does not have enough funds when they have to deduct monthly premiums. After a lot of back and forth where my policy almost lapsed they deducted but a higher amount from the usual monthly premium. They later on apologised for the error but did not credit me. Now ending month of Feb there were funds in the account but the debit order bounced still which led me to incur further charges. Am really frustrated with FNB life. I just don't understand why can't they get my account into order. Now all my funds are gone but the monthly premium was not received.