If the call threatens anyone, yes. If the call is traced, you could be arrested if the content of your call was harmful too. You may not stay in jail, but you would get a record which could harm your future. Is it worth pranking someone? I don't think so.
It depends on the call and who you call. If you keep calling the same person, that would be harassment and you could get into legal trouble. You could also get into trouble if the calls are threatening.