International customer failure

Vodacom is making my life he'll! I have been out of SA and calling everyday for a cancellation of a contract because I changed my roaming plan but they are not willing to cooperate. When I call their call centres of which they said I should call after a lot of emails with no information they say systems are not working I must try calling later , this happens every time I call them. My SA number cannot recieve calls but can make calls, they still say they can't help me.