Why is my atiel so hard to train HELP!?

hi people, ive had my atiel for about 6 weeks now and hes still not tame =(. he/she can get on your arm brilliantly now and munches away at his millet, but then when I say off he does but then he instantly turns around and trys to bite me =( I have just started to touch his beak and try to stroke his head and he still doesnt trust me but its all new to him so .... but please help coz my mum wants to get rid of him plzzzzzz HELP ! ! ! ! ! ! !