You're right actually. The post doesn't mention whether it was the bank or the sheriffs office that goofed on the name. He also mentions something about his credit union being more competent. That suggests it may have been the sheriff's office that mixed up the names if two separate banks had garnish orders.
It seems clear that its not a mistake of one party or the other, clearly its a mistake on both parts. The Sheriff should have checked better and the bank should have double checked.