Terrible Customer Service

On the 17th of April I was debited for my installment and to my surprise I was debited an additional R600. My contract advised that my installment is R399.87 but I later found out by phoning in that my cellphone was not added correctly in the beginning and the additional amount for my installment was not communicated so you can understand my surprise when I was debited over R1000. I have called several times from the 17th of April till today the 6th of May which is almost 3 weeks. I demand a full refund of both installments paid and request my policy to be canceled. I have requested to speak to a manager since last week with no joy. If this is how you treat your new customers I would much rather take up a policy else where.