Laughing, Talking, Joking with Non-Mehrams is not a Hijab;

with the men, but thats not right, even if he is the Shaikh.Allaah says: “. . .
then be not soft in speech,
lest he in whose heart is a disease should be moved with desire, but speak in an honorable manner.” [al-Ahzaab:32]

So talk to them when there is a specific need, and in a manner that is not necessarily rude, yet it is polite but firm.

Staring at the brothers or checking them out is NOT Hijaab;

Allaah orders us to lower your gaze in the above verse. Why? Because a single look can say more than a thousandwords.

So, even if you are properly covered, keep those eyes down, conduct yourself with Hayaa, and avoid fitnahChatting on the internet/phone is not part of Hijaab;It is haraam for a man or woman to listen to each others words with enjoyment, for fear of fitnah (temptation)
There is no such thing as were just friends.

Talking to non-Mahrams is wrong even if it is through the internet ortelephone.

There are too many stories of illegal relationships, fornications, broken homes, extra-marital affairs and runaway brides to even mention.
That is why inIslam anything that leads to haraam is also haraam.
ALLAH says:Do not (even) come close to fornication, for it is an indecency, and its way is evil.
(Surah Israa:32)