Poor Customer service

I've changed my debit order date with 3days and now instant life is charging me double installment with the excuse that I was always paying in arrears because my pay date was the 25th. This does not make sense to me as I paid from inception everymonth. I asked for a proper breakdown from beginning to now so that I can see why they say I've always paid in arrears, but Ashan Naidoo just ignores my requests and replies with the same thing everytime. When I asked that a manager please answer my query, then my mail is just ignored completely and the double debit order just went through. My husband and I took out our policies together and pays together from same bank, yet his is not in "arrears" by mine is?? I want the extra installment reimbursed or I will start looking at other insurance.