ADT bad service

We arranged for ADT to come and quote us on installation for our alarm system at our house. We had the equipment, just needed to see if everything was in working order and to get activated. The salesman came out ontime and was very helpful, our sliding sensors needed replacing and quoted us R350.00. We in the meantime found the missing part of the sensor and the salesman said we would not have to pay anything for the installation. Technician booked for installation the friday afternoon, couldnt give us an exact time, would call an hour before The technician phone just after 11am and said he would be there by 12.30, only arrived at 13.00 rushed through the "installation", one of the sliding door sensors didnt work, said he was late for his next appointment, didnt complete the installtion or give us a pin to activate or deactivate the system I phoned the salesman on monday to inform him that the system was not functional and what had happened the friday, he said he would sort everything out asap 2 days later technician comes out, installs the new sensors, which we think will be the R350.00, then presents us with a bill adding R438.60 for labour. I now queried this with the sales man, as the installation was not completed in the first place and it was not out fault, so why do we now have to pay for labour Salesman said that the invoice is correct and we have to pay for the labour Im really not impressed by the service received so far, and would like to know what the cooling off period is and my rights to cancel this contract