Don't upgrade mobile contract early

After receiving a sms from Telkom that i could upgrade early, I upgraded on 12 June 2015. I had already paid the billed amount on my old device for June. On receiving my July bill, I noticed that the amount charged for the \Device instalment fee"on the new device was charged for June as well as July. A query was logged at Telkom Clearwater and a reference obtained. Another sms was received to say that the reference was closed. A further sms was received saying that the full amount (including disputed double fee) would be debited at the end of July. A further trip to Telkom Clearwater was made on 27 July as no explanation was forthcoming. I was told that even though the contract was upgraded early"