I thought I understand the thing with the margin-call but now I read on the Oanda-Page this:
It is not a good idea to get a margin call. We suggest that you take proactive measures to prevent getting a margin call on your account. Overall, we recommend that you use a lower level of leverage. This makes a margin call less likely.
Why it is less likely that you get a margin call with a lower leverage??
Because with a lower leverage you must pay higher margins and this makes a margin-call more likely...or not?!?