As already mentioned to you in other posts, you can never guarantee that any parrot of any species will actually talk...There are many African Greys, Macaws, Cockatoos, etc. who are male and never say a single word their entire lives...
I'm sorry but you keep buying birds and then when they don't start tallking very quickly you sell them, return them, whatever it is that you're doing with them, and then you bring home another one and do the same thing when it doesn't talk...You need to realize that not only can you not guarantee that any parrot or bird will ever talk at all, but you also are buying young birds that haven't even gone through puberty yet, and you're expecting them to talk within a certain amount of time or you get rid of them and replace them with a new young bird...You aren't giving them nearly enough time to begin talking, some birds who eventually become great talkers and learn hundreds of words and phrases don't say a single word until they are a couple of years old!!! So if you keep doing this you're just going to keep getting the same result...And as Ekkie stated above, these are parrots with the intelligence of a 3 year-old human-child, and you're treating them like they are a defective TV or a used car or something...That's not being a responsible or caring owner at all...I know you're from a country with a totally different set of beliefs, ethics, practices, etc., however plenty of people from your country come here for help with their parrots, and they love them very much and take great care of them, including getting them Vet care, and they love them very, very much...So in this particular case the cultural-differences between you and people in the US, the UK, Australia, etc. do not provide a valid excuse for what you've been doing with your birds...
If the only reason you want a parrot in the first place is because you want a pet that talks, which is how what you've been doing makes it look, then you shouldn't be getting a pet parrot to begin with, because what you are continually doing is harming them emotionally and very likely causing them to develop Feather-Destructive Behaviors like plucking, and even Self-Mutilation...Plus it's just ridiculous because not only do you have no way of choosing a bird that you know for certain will talk, but you're getting rid of them after only a very short period of time and while they're only a year or two old! Half of the parrots that you have already returned or sold are probably talking up a storm now that they're older and have had enough time to learn how!!! (for whatever reason, I have no idea what benefit a talking parrot gives you over a non-talking parrot, but you definitely have some reason),
