Delays by Vodacom to cancel the handset insurance

1 July 2020 I phoned the company that insurers Vodacom's handset to cancel my handset insurance. I told them that I will not afford paying for the insurance anymore hence I am phoning them on the 1st so that I don't pay end of July. I asked them if there is anything I need to do from my side, they said No, someone from their side will phone me to complete the process. I asked them about timeframe, they said they don't know. They couldn't even give me an idea. I explained to the person that I was talking to that as long as they wont delay unnecessarily so that I keep paying. Today is the 12th and I haven't heard from them. 2nd, I have just received my invoice for the end of July and the insurance is there. This is unfair and I feel they are doing this intentionally to keep us paying. Why cant I just write a letter to cancel and give them a 30days notice?? Why is the cancellation process depended on them?? So if they take 3 months it means I must continue to pay for something that I can no longer afford?? I will not have money to pay for this end of July please help