Language can be slow to catch up with changes in society, for example, we still talk about ringing someone up, even though phones no longer have a little bell attached as they did in the "good old" days, and we download "ring tones" for our mobile phones, even though half the time they are snippets of popular songs. We also talk about dialling a number, although we no longer use phones where you have to put your finger into a dial with holes and move it round, but we don’t say we press or type a number, even though that is exactly what we do.
In some countries people answer the phone with a simple ‘Digame!’ or ‘Tell me!’ In England we usually answer the telephone by saying who we are. When you phone someone at home you might be greeted with something like, ‘Hello, this is Margaret.’ or if you phone a company perhaps more formally, ‘Good morning , Hardy and Company, James Brook speaking. How can I help you?’ That said, "hello" or something similar is used by millions of people right around the world, from Hola to Hallo.
But the word "hello" is relatively modern, and horror of horrors it's an Americanism. In Britain people used to say "hullo", so although language can seem stuck in the past, it does change. You might not know this little snippet; there is one instance of the word ‘Hello’ being used by Mark Twain in 1872, however it did not come into wide use until later when people used it when answering the telephone - a practise begun by Thomas Edison.
Hello, formerly an Americanism, is now nearly as common as hullo in Britain (Say who you are; do not just say 'hello' is the warning given in our telephone directories) and the Englishman cannot be expected to give up the right to say hello if he likes it better than his native hullo. - H.W. Fowler,A Dictionary of Modern English Usage. 1926
I wonder what telephone language is used in places where phones were late on the scene and so people never had the opportunity to use those lovely Bakelite phones with circular dials and little bells.