I do not really have the reply
I was given HTC mobile phone bought from Aeliotis in Cyprus as a present from my bf for the price of 499euro. When I switched on the phone, in the "welcome screen" I could see the logo of T-mobile (a German provider) operating networks in EU and USA. In this way, I realized that this phone was an unlocked phone. Also note, that the box had already been opened when my friend bought it and the instructions as well as the notes on the box were in German. Also, my friend told me that the seller at Aeliotis switched on the phone before giving it to my friend.
The next day, I went to their shop the with my friend, asking them to give our money back. At first, when I told them that the phone was unlocked, the person at the customer service desk was saying that he had no idea what I was talking about. After 5mins of discussion they gave us our money back.
Later, I bought the same phone (in a sealed box) from the HTC agent in Cyprus at the SAME price of Aeliotis. When I told them about my experience with Aeliotis they told me that Aeliotis or any other company can sell HTC phones in Cyprus but they don't accept to repair any faulty phones etc at their service department if the phones were not imported by them (in some cases they have to pay 200euro or so). Therefore, in these cases, the seller needs to send the phone back to the exporting country.
In general, unlocked phones may not have any problem BUT among other things in some cases due to proprietary settings sometimes installed in locked handsets, the phones don't always function correctly with other carriers. Also, there is a risk with the warranty and the service dpt. If you need to send the phone back to the exporting country for repair it may take anywhere from 1-4 months to get it fixed (IF).
So, why should I risk buying an unlocked phone when I have the option to buy the same phone at the same price from the official agent?