Adt service unreasonable

Adt service are really good in my area, but it is really unacceptable to be charged R650 exl. VAT. So that a technician can come out to replace a censor's battery. Then you obviously have to add the price of battery to that as well. I think I pay enough each month that they can come and replace a battery without being charged an arm and a leg. Will definitely be my main reason to search for other service provider once my contract expires.