Hey i sent my uno cento in for a service today. They said it costs 900 rand, okay well basicaly they said i need alot more done. 4500 rands worth. Is it worth paying this i no the car will be running great after this but I mean its very expensive, considering i only paid 12 000 for the car. I could sell it and buy another uno for about 15 000. So what should i do?
This is impossible to answer specifically because you haven't said what's being done
Generally you'll find that most of us on the forum do at least some degree of work ourselves on the Uno. Certain jobs (e.g. changing the front wheel bearings) are very difficult or impossible without certain special tools (e.g. a press). But this is the exception. Most jobs are easy on an Uno - changing oil, changing spark plugs, etc. - compared with bigger, more complicated cars, and their V6 engines, automatic transmissions, etc.
But to try and answer your question in general terms. It costs money to maintain ANY car and keep it in good condition. It will cost a similar amount to maintain (and by maintain, I mean 'service') the Uno you mentioned that costs 15,000. And if you skimp on maintenance, at some point you'll sacrifice reliability, performance, economy, safety, and resale value. That's a lot at stake when you think about it.
The average age of an Uno worldwide is probably about 15 years. At this age, the car itself isn't worth very much. You have to expect to spend quite a bit of money to bring a neglected example 'up to scratch', usually MORE than the car is worth. And that isn't money down the drain because it puts the car into a more usable state (and, still costs less than buying a newer car). It's easy to think that you could just buy another car, but the reality is that they will all be about the same average condition (with a few mint-condition-one-owner exceptions; but you'll know about those because they will be more expensive to buy...)
I'm guessing that your Uno Cento isn't all that old compared with most Unos in our countries. And there's probably nothing much wrong with it. In fact, we'd probably kill to have a (1997? 2000?) Uno like yours for that little amount of money

12,000 Rand is only about NZ$2000, which is 780 pounds, folks

And unless it's lived on the Durban seafront, I expect it has no rust either, since it doesn't rain for weeks at a time!

However, we have no idea of how it's been treated in the past, or how the car is running.
So the answer to your question is Yes, and No.
Yes, because, assuming the work is necessary and being done properly, it's certainly worth paying - you're spending less than half the value of the car to bring it up to scratch and assure you of reliable, happy driving.
No, because, we would rather know exactly how our maintenance was being spent and how it was carried out (speaking here on behalf of other forum members who work on their own Unos

)
Hope this helps put it in perspective.
Cheers,
-Alex