Many Japanese people speak 「～じゃないよー」「～じゃないもん」「～じゃないっ !」to friends.
But when hearing people from foreign countries speak 「じゃありません」,I can’t help thinking they are from LOWER class. I don’ know why. But it sounds dirt. (I’m sorry, my English is too direct.)
I think the combination 「じゃ＋ありません」sounds not good.
When I say 「ありません」, I speak politely. So I say 「～ではありません」
When I say 「じゃ」, I speak very casually to my friends.
Some Japanese people say 「じゃありません」, but I think it’s a bit difficult for Japanese learners because it depends on the situations.
Anyway, I’m sure that most Japanese people see 「じゃ」and「じゃあ」dirt when people from foreign countries say it.
I don’t recommend you to say it.
If you are from LOWER class, I think you can say it.
When you speak to your close friends, it's OK.
But I think you should not write it.
I’m sorry, my English is not good!!!
