I think you can do a quick assessment on your own first , only when the figure deviated too much away only you engage external party. To assess, just do the following :-

1) list down all your house appliances

a) AC ( kW rating ) x qty x hour of usage / day
b) Refrigerator ( kW rating ) x hour of usage / day
c) rice cooker ( kW rating ) x hour of usage / day
d) washing machine ( kW rating ) x hour of usage / day
e) TV ( kW rating ) x hour of usage / day
f) iron / electric kettle / oven ( kW rating )x hour usage /day
list down all you can

2) After that sum the kWh usage per day up x 30 days .

If the figure come close to 1300~1500 kWh, then nothing wrong . If the deviation too much, then yes, something wrong but it shouldn’t be internal wiring issue but more on illegal tapping after your TNB meter .

If don't have SIRIM then go for the reputable brands like - Carlo Gavazzi , Siemens, GE . Mikro local product are well accepted in the industry if not mistaken. If not reputable brand, probably you need to send it for calibration before the installation. Sirim's Lab is doing calibration for the measuring devices to my understanding.