Telkom/Sell Direct faud (again)!

Once again I've been duped by SellDirect/Telkom. My monthly installments were agreed on at R119.00 I've now received an invoice from Telkom for R201.87. I've received the device but have not used any data as I'm still using my MTN SIM card. I would expect an invoice for R119, not R201.87. I would like my device to be collected and a debit of R119 to be deducted on 1st October. I'll then make alternative arrangements for obtaining a new device.