VODACOM, how do you justify taking my money and threatening me for not paying for this lack of service?

In December 2017 I noticed the signal at home was switching on and off... It got worse and then eventually there was no signal at all. i called Vodacom asking for help almost every week, which then turned into every 2 days. All I got was: "this has been given to network team and you will hear from them in 2 days", then I would hear nothing and when I called back the query had been closed. This carried on like this for months, no service, but they charged me every month. Eventually I asked for them to cancel my contracts which they said they would do, but then could not get that right either. I requested a refund on my payments from December, and Eventually they sent a technician to my place who confirmed that there is a signal issue in the area and that I would get a report the following week. That was 2 weeks ago, still nothing. I instructed the bank to cancel payments, and reverse the latest payment, which they did. Today I phoned Vodacom asking what is going on, they told me because my account is in arrears they can no longer help me, and they will be handing me over and it will affect my credit rating. They expect me to pay for no bad service and no signal!! I refuse to pay for bad service!!! VODACOM, how do you justify taking my money and threatening me for not paying for this lack of service?