******** bill surges

My bill has hiked incredibly the last 2 months. I went from pay 250-300 rands to 800 rands and when I inquire they want me to pay a fee for them to investigate. I live alone in a bachelor flat and don’t understand how my bill is suddenly soo much when I spent almost 2 weeks away from my place in the previous month. None of it makes sense and paying for them to investigate is a **** of note.