Change group visa to personal one

Hi, we were granted a group L type in Hong Kong to enter China with my friend, but due to circumstances I need to leave earlier. However, the requirement is that you need to enter and leave the country at the same time. Do you think it is possible to change our group type into L-type at the PSB in Shanghai? (I need only 14 days, my friend 21). We have already spend 60 days on a L-type before.

Any advise is welcome! Thank you!!