The best you can get when switching operators, is the same number, but a different prefix, ex: xxNNNNNNNN -> yyNNNNNNNN
Not necessarily true. At least in some -- but probably on most -- European countries you can keep the whole number when changing providers. I have done that in two countries. There are web pages where you can check which network a particular number belongs to. Prefix is not a reliable indicator any more.
The best you can get when switching operators, is the same number, but a different prefix, ex: xxNNNNNNNN -> yyNNNNNNNN
Not necessarily true. At least in some -- but probably on most -- European countries you can keep the whole number when changing providers. I have done that in two countries. There are web pages where you can check which network a particular number belongs to. Prefix is not a reliable indicator any more.