Credit days

Hi

Yesterday I had an incident. I got a contractor to do repairs and paid 50,000/- advance and after the work is completed he's asking me his balance 1,50,000/- ASAP???? WHY? all companies run on credit as per working capital. I cleared it today. My question, is there any under section that I can explain a contractor in the future that establishing credit days is mandatory as per the statutory acts. Plus I'm holding payments to improve my working capital. 

Txs