Receiving amount due statements even after contract expires

So much ********* service provider. Few months back (around december) my contract with vodacom expired. I called vodacom and was instructed to pay last month due and then they will terminate the contract. I paid and called again and was informed that it is terminated. The phone number (account no: I***-0) also stopped working. Problem is no ended here. I am continuously getting statement that I owe some money to vodacom. I am so much frustrated with their ethics and integrity.