Bad service

I phoned Finrite cellphone insurance several times requesting them to debit from my account. I even sent them an email with my banking details instead they only deducted one premium, and never deducted the other money that I am in arears with, I was in arrears because of their fault. I changed banking details and they never debited on the new account. Last month I spoke to one of their agent who gave me assurity that they will deduct the money which was in arears. She also advised that I send an email which I did, but the company is failing me. It looks like they want to **** me all the money I have been paying for last few years that I have been paying.