Charged my account 2.5 times amount without authorisation

I signed a home data router deal on 27 July. Package R399 per month. I had to pay in advance before they would deliver sim and router. Sales woman charged me pro rata for July plus the full month of August. So my next payment I authorised for a debit order would be end of August for September, amount R399.

Today, a debit order of over R830 was put through my account. Completely *******ly and not even remotely connected to the package I signed. No one works over a weekend to help or responds to emails. Completely shocked as I've literally had the service active for 6 days.