Atrocious Helkom

My wireless contract has ended 22April 2018 and I have been trying ever since to cancel it but to no avail. I have even gone in store where a manager has felt apologetic and tried to help me by sending off the cancellation forms but still to no avail nothing has come of it. My account is still being billed and I'm unemployed. When I log online my 2 accounts don't show so there is nothing I can cancel, please help I'm desperate, what can I do?