Yes, you can trust most sellers on eBay. I've been on eBay since 1998, buying and selling a little. Most sellers describe their items and tell you of the flaws. Do your research before buying. Check their feedback. If you see that they have negative feedback for not being truthful in descriptions, or negative feedback for sending items which are broken, dirty, etc., then don't buy from them. And if you are purchasing clothing and are allergic to smoke, make sure to ask them if they are a smoke free home if they do not write that information in their description.
On a cell phone, you do need to be more careful. Those of us here at Yahoo Answers can't say if it will be defective as we do not know the item number or the seller. Some people selling electronic items are scammers. Again, you need to check their feedback. How many positive feedback they have, how many negative, and what are the reasons for negative? Also, check to see if they offer refunds if you are not satisfied. If they have a lot of positive feedback, then I would go with it if they offer refunds if you aren't satisfied, and if they have at least 100 or more positive feedback with no problems. But again, I have not seen the auction or have any idea of the seller, so I can't make this judgement for you.
Be sure they offer a form of payment you can use. Some sellers only accept Pay Pal. If they do, make sure you have it before you bid, as you can get a negative for non-payment if you don't have a way to pay for the item. DO NOT wire any money, ever, as this can be a scam. I would not recommend purchasing electronics items from outside the US either.
I hope this helps.