Is it possible to cancel paper submission after one week? I submitted my paper one week ago to a journal and I want to cancel my submission. Is it possible?
It's certainly possible.  You can withdraw a submission at any point until it has been accepted and you have signed the publishing agreement.  You might upset the editor, but there's absolutely no way they will try to forbid you from withdrawing the paper.  The worst case scenario is that they will remember you as a flake who wasted their time with an inappropriate submission.  (Of course, that's not a good outcome.)

You should not plan on resubmitting the paper to the same journal, at least not if the social conventions in your field are like the ones I'm familiar with from mathematics.  There might not be a formal rule against it, but it would look really strange, and you'd get reactions along the lines of "What are you doing?  You had your shot at publishing the paper in this journal, you deliberately withdrew it, and you wasted everyone's time in the process.  Now you want to start again?"  (Only it would probably be stated less confrontationally.)  I doubt they would accept a resubmission unless it was a really important paper.

The disadvantage of withdrawing a submission after just a week is that it looks flaky, like you couldn't be bothered to check the paper carefully enough last week to detect the problem.  On the other hand, the longer you wait, the more time may be wasted by reviewers.  If you know you need to withdraw the paper, it's better to do it early than to delay.

Note that everyone will assume you withdrew the submission because of a serious problem with the paper.  If there's a minor problem, correctable without important consequences, then you could submit a revised version instead of withdrawing the paper.  (That would still look a little flaky, but less so.)

If there's no problem with the paper itself, but you just changed your mind about where to submit it, then you'll really annoy the editors and reviewers.  You shouldn't do it without a compelling reason, and I'd recommend not pointing out that you merely changed your mind (since there's no sense in adding insult to injury).  This would make sense under some circumstances, for example if you discovered you accidentally chose a predatory journal, but under ordinary circumstances it would really look bad.  You could still do it, but I wouldn't advise it unless you feel you really made a dreadful mistake in choosing the journal.