Unfair demand from cartrack

After complaining on hello peter I was given a cancelling letter but everyday since then I received 40 calls in day from them demanding money and now I been treatened with my account being handed over to my surprise my account had lapsed on last day of October according to their call centre so I told them that I will no longer renew my contract because I cannot pay my monthly fee of R245 and R402 for renewal at once since I have financial constraints so I will not will not renew now they need a R673 the fee which I never agreed to be debited from my account I have reverse the same fee twice.