Telkom debited more money

I'm very sad and disappointed with Telkom. For the past 10 months I was charged R399 for wifi router as agreed with Telkom and myself. To my surprise last month I was charged extra R29 and this month I was charged R663 instead of R399 and I don't have any subscriptions. I no longer want Telkom to debit from ny account, I rather pay them via eft ir at shop. Please assist I'm disappointed