Contract dishonored

Hi I have made cantact several times from last year October until to date for them to send someone to repair my tracking unit, everytime I phone they say they sending a mail to repairs and will get a call to arrange time and date, this has not happened yet. This has a negative impact on my insurance as I'm responsible for making sure that the tracking unit is in working condition. Therefore after several failed attempts with car track, I requested that they cancel my my contract as they have not honored their side of the contract and asked them to do so without me having to pay cancelation fees and they have refused to do so. Please assist me in this matter.