Hyundai Motor India — Lack of spare parts and prolonged wait even after advance money deposit

Address:

Kangra, Himachal Pradesh, 176061

I own a hyundai i 20 asta 2010 model. And on 17/05/2016 i noticed my abs sign flashing and not going off while driving. Alarmed of the situation of malfunction in abs i presented my vehicle at sant hyundai, ghudkari kangra (Hp). Mechanic service/engineer checked it thoroughly and explained that one of the hub of rear wheel (Part of abs system) needs replacement. At that time the part was not available with them and i was surprised that they were not ready to get the part ordered unless i deposit some money with them. As i'm worried that how ever trivial but it was a malfunction in brake system i deposited rs 1000, as advance money wide receipt no 24356 dated 19/05/2016. Till date i'm waiting a call from the workshop to get my defect to be rectified. On enquiry about said part i am told that the part is still not available and i can drive my vehicle without any concerns of safety.
Is it really not important to have a functioning abs system in vehicle.
And if it is required in vehicle then why don't they keep such parts in inventory.