If the court told you to go to the court, you'll have to go: they will likely not accept (or worse--take but not properly credit) payments made through their payment system. And if there is a warrant out for your arrest, you need to deal with it--it will not go away even if you paid the underlying fine, but rather needs a judge to cancel or void it. Hire a lawyer to assist you with this: you do NOT want to be arrested due to misdelivered letters.