Tata No Parts 6 Weeks and Counting

I bought a Tata Super Ace thinking i would get good value as long as i took out a maintenance plan. Not that it helps, they never have parts if when you need them. Currently my vehicle has been at the panel beater for 6 weeks as they do not have spares, an isolation radiator, bracket , evaporator pipe, this was promised on the 16th July, now month end and i am trying to run a business that need a delivery vehicle. Surely you should be keeping all sorts of parts as a standard stock, this is not acceptable