Ladies Ignorance about Cars...Unfair thoughts

I was shocked when the staff at the garage reception of my car company handed me the paper where the specified amount to be paid for at 20,000 km.check-up was morethan Qat.Riyal 1600. Whilst before i leave my car for them for checkup, i asked how much would it possibly cost me. And i was told that it is around 550 Q.R. and if there are any defective parts we are going to inform you,so i left my car with the thoughts that it might cost me more or lessthan a couple of hundreds more. At night that day, i was informed that there are parts like, brake pad, filter, gasket,spark plug, genuine oil,element sub-assy,pad kit front, and rubber wiper(eventhough, i've just changed it a week ago)to be changed. And the hard thing was, i was ask if i wanted the battery to be replaced there or in Industrial.I asked what is the difference if in Industrial or in their branch near the Mall.It was explained to me that i will get it cheapper from Industrial by 60%.I refused to change the battery because i doubt if it really need to be changed at 20,000kms run. And it is starting smoothly, my car is landcruiser and never use the cooler, or even tried to turn it on. I seldom go out at night where lights are needed in short, it is likely that battery is being used only as starter. This is my first car in this company, buti have other cars which are all company maintained. What i wonder alot was this is the only company that charge alot of money, and change alot of consumable parts every check up. Since the first 5oookm. check i made in this company, they take much charges i don't even see. Could anyone out there, especially kabayans help me clear my doubt of being over charged? Do this management in this company thought that because i am a lady, i know nothing about cars but cosmetics? I have more expensive car than this and have a less expensive one too,and believe me, this less expensive car that i have is a darling, (i am not endorsing) but,the company had the brake pad changed only once just recently. I also do the regular 5000km. check but i pay only for the filter and filter oil or assy oil.Spark plug was changed only once in two years, and it's for free. Does this Toyota Co. management in Mall roundabout branch doing fair or some sort of abuse to an ignorant lady like me who seem doesn't understand about cars.