You should not sign a contract for even a month There can be profound consequences, as you may lose security, money, infrastructure, property and mental peace. Thats because being guarded by a service which is not able enough is as good as giving off money for nothing.
Security services do not essentially have to come in a patrol car. Guards may also monitor the place in cars or simply walk and do the job. You will know more about it by seeing videos of such guards on duty.