I have to phone every month for incorrect deductio

My bond increased. I phoned and informed them it is impossible the amount. They informed me because the term is short they had to increase it more. What the hell? It had to increase with the balance and not the term. They did rectify the error and since then I have to phone every month for the incorrect amount to be refunded. How difficult is it to rectify my instalment? I had ref ***4, ***. I had to phone again today and the amount is even more now? The service is terrible. Yes I get my refund when I phone but why should I phone, why not fix my premium? Who is going to pay my telephone account? REF: (***2