Nedbank Global Division in Johannesburg

For the last 2 months I have been sending funds to our Foreign Head Office, and for the last 2 months Nedbank Global Division have been UNABLE to give me a CORRECT Rate of Exchange. I have no idea how they calculate their Rates of Exchange. UNBELIEVABLE AND SHOCKING !!!!! Companies transferring funds overseas be VERY careful of the rate of exchange that they quote you on.