inventory update error

we use Mb1c for one material one batch, quantity increase from zero to 12000, now we want to add quantity to 12300, when I use mb1c, move type 501 to this batch, it says: A goods receipt has already been posted for this batch.

and further Account determination for entry MY00 GBB 0001 ZOB Z021 not possible

Message no. M8147

we can't change obyc setting, so how to add 300 quantity?