New Puppy keeps biting!?

SO we have a new puppy. He's a A Jug [jack russel mixed with pug] he's a hyper little thing who loves to test us. We've had for about 3 almost 4 weeks and he's almost 3 months. now he is teething and he has TONS of chew toys! we even got baby teething rings and we freeze them for him. But he still insists on biting our feet when we walk. we scold him we say OW really loudly we stay consistent. but he just won't get it that it hurts! Please help!