Vodacom contract ****

I have been asking vodacom to know when my contract ends as I believe my contract ended in April but you keep invoicing me. I asked in March as I wanted to pay and cancel future contract but you have not responded to my emails. Now I see am being billed for may and June. Which I can't even use the airtime am billed for because the account is blocked. I spoke to customer care on Twitter and am told to call customer care using a vodacom phone sim, which they blocked. So how the hell am I supposed to contact them because I will not use my airtime. Twitter customer care can send correspondence that I wanted to cancel the contract. Vodacom just wants to **** me further. I refuse to pay for the airtime I ddnt use. I ddnt even use the February, March and April one.