Poor service delivery

I have a contract of 36 months with Vimba Security Services. Their alarm always does not have a signal, they have sent a technician which I had to pay extra for and still the alarm its not working. They promised to replace it with a new one at no extra cost but failed to do so. I pay my monthly subscription with no fail and this is type of service I get? I'm tired of complaining and nothing happens.AR80489