If you are having an old mobile phone which is not in use right now, you may sell that online and get some hard cash. Since that mobile phone is not in use and just getting dust in your drawer, you can sell that out and that will be utilised to build latest phone. There are lot many websites where you can sell your old mobile phones, even you can check the current price offered for your mobile phone model.
Here is the list of websites where you can check the offered price for your model,
Here you can search for the model number of your mobile phone and then they will show you the current offered price for the same. You can choose whether your mobile phone is in working condition. It is not in working condition, they will offer you a new slashed price. But for a non working phone, whatever you get is an earning.
Here you can compare the prices offered by different traders at a single place. After that you can use any of them to sell you phone.
Same is the situation with this website as well. You can check the offer based on your mobile phone model and then send your mobile phone to the address and then you will get some hard cash thru PayPal.
This is also in the same business where you can compare the price offered by different traders and then you may go any of them. Some traders offers gift vouchers but some of them offer hard cash for the deal. Cross check that before completing the task.
Prices offered by these traders are not good enough, for example Nokia N95 in non working condition will be offered at ~ Euro 45 ($30) which is not enough for Nokia N95 for sure. But still if you want to try with some of your unused phones then you can do it instantly.