In Blue Label Telecoms

My husband took out a cellphone contract about 4 years ago and last year they notified him that the cellphone was paid in full and that he should upgrade so he did so but up to date we never received the new upgrade and somebody signed for the cellphone. We asked them for a statement which they cant provide us with,they keep on sending messages that they cant find any record of payment but each month they took the installment.End of last month they deducted twice the amount of the installment which is unacceptable