Just called USCIS 10 min ago to request 485 transfer from one 140 to another 140. got two answers.
The 1st call was transfered to a guy. This guy is not friendly. He might not understand why I want to transfer 485. just tell me to follow the instruction in the 140 approved notice, and 'thank you for calling USCIS' then hang up.
the 2nd call was transfered to a lady, who is very nice. She told me I must write to USCIS to request the 485 transfer.
Conclusion: write to USCIS (just as Pjiang recommended), If you are lucky, your 485 can be transfered. if not, file another new 485.