Incorrect billing

Im having a problem with my billing, I contacted Rain services and asked for a hardware update for the 101 device . I was advised that they do not have that option and I have to cancel my subscription and apply for a new one. I did that and a payment of R819 was paid in April, the device was collected. I connected the new devise on the 1st of May and I was expecting to pay the new subscription of R649 and to my surprise my balance was R1500. I sent a query for the billing and it was corrected to R1084. I want my billing to reflect the correct R649 as per my new subscription. If same cannot be done please cancel your subscription and collect your device. Thank you