Replacement contract

I lost a phone(October) i had and was advised that i may take out a replacement contract with Telkom. The agreement was i will be paying the remaining portion of the lost device in monthly installments and pay for the new device as per normal contract terms. I noticed the invoice for November was not the amount that i should be paying as it had included the whole amount of the previous device and i contacted the call center numerous times to try and have this sorted before the date for the debit order but there has been no solution to my query. The only response i get is my case has been escalated and the response time is "i will receive a response by the end day or 72 hours. My frustration is the fact that the debit orders (Not only Telkom) bounce and i incur the charges and to top it off my line has been locked. Another update i received from the consultant i took the device was that the previous device will only be paid in 3 payments and not the agreed monthly installments.