Let's agree that 'if you are in Paris, then you are in France' ($A \implies B$). (We could get picky, and say maybe you're in Paris, Texas; but let's not!).
But then the converse ($B \implies A$) is not automatically true: for example, we can't then deduce from 'if you are in Paris, then you are in France' that 'if you are in France, then you are in Paris'. In that sense you're right that 'it's not logical' to say the converse is always true.
Now, bear in mind that the converse might be true, or it might not. It must be proven either way based on other information. And it turns out that we know enough other things, about European geography in this case, that we can also prove that the converse is not true.
On the other hand, what we can always deduce is called the contrapositive: once we accept the truth of 'if you are in Paris, then you are in France', then we always automatically can say 'if you are not in France, then you are not in Paris' ($\neg B \implies \neg A$). That will always be true (at least, in the world of mathematical language).