The representative at the desk added on an insurance, which I learned about AFTER my booking- it is called "Roadside Protection", which he added at the same time as the toll charges (he mentioned the toll charges and i agreed to this). This was despite me saying I wanted no insurance or excess reduction.
- Update: following the below reply, Sixt has reimbursed the charge and issued me with a voucher to rectify the situation. Very grateful for a prompt resolution. Thank you Sixt