Thank you guys. I could challenge both GLD and PLT!

I wanna share my experience below.
1 I called AA's Tokyo office to sign me up Challenge for PLT, yet the rep insisted I could not PLT, because I was not GLD, or I could not challenge with AY or so...anyway, I signed me up GLD.
2 After that I mailed AA's headquater by e-mail, 3 times or so. Finally I could sign me up Challenge for PLT. I had thought that I could cancell GLD, yet as some one had already mentioned, they might not be able to cancell any Challenge, I am sure.
3 I flyed KIX-HEL-OSL, ARD-HEL-KIX by AY. and I could be GLD in HEL-OSL, and I ould be PLT HEL-KIX. Namely, I could get bonus miles HEL-OSL, ARD-HEL-KIX!

I was so surprized yet satisfied. However, before I checked my status, I was worried about whether I could sign me up or not. It was a gambling. If you think it is a worth doing, try it!

reikkonen