Bad customer services

I bought a car on auction on the 27th June. A salesman connected me to finalise the deal. On monday the 30th June we spoke and he informed me the car is not staying on he thinks it is the battery. The mechanic checked as well and he will arrange for a new battery because the car was standing for a long time and he tried to put battery booster on and still the car is not staying on. My brother arrived from East london to fetch the car and he was given the car with the new battery but battery light still showing on the dashboard when the dekra report mentioned nothing of that. When my brother tested the alternator it showed faulty parts in the alternator. The mechanic could not have missed this if another mechanic picked it up with 1 check. We buy cars springfield ****med me knowing how expensive an alternator costs. I reported this to salesman and logged a concern and my claim was rejected. This is not the only incident i bought a car from richmond branch as well the car came on a truck to east london and the tape was removed before it was loaded on the truck i reported it as well and claim was rejected. I dont understand how i am such a loyal customer but get treated so unfairly