Well, I never had such problem. Anyway, it’s not really people who are spamming your website but bots.
One way to block great part of your spam is to use a plugin like Akismet.
Also, you could try to go your phpMyAdmin tool, choose the right database, then search for that post. If it still exists just delete it permanently. But I really don’t recommend this, you might actually do something wrong. Or, at least back your website before you do it.
