Question is the topic.
So is it CEX.IO, Blockchain? Or maybe ATM BTC machines that we have in our country.
Cex.io is an exchange. Blockchain.info is a wallet. Using the wallet you can only store BTC. With the exchange you can buy or sell them. In case you use Cex.io and want to exchange Bitcoins to fiat, you can either trade on the website or use the buy/sell section and then withdraw funds directly to your Bank card.