Yoco taking more fees than agreed!

Everything went so well and had fast responses when purchasing and registering. However according to the information provided, Yoco would subtract 2.7% of each payment I receive. They are however subtracting more. For instance, i received a payment of R350, of which 2.7% is R9,45, however Yoco subtracts R10,87? On a payout for R580, R18.01 is subtracted, however 2.7% is only R15.66. Tried using their whatsapp line to chat to someone to get answers. It's been 7 days and have received no responses!!