Hi Zoe. I'm not sure I fully follow what you intend, but here's my best interpretation:
Are you asking that the September production/deliveries be brought forward to August?
If so, please let me know as soon as possible, otherwise it will be very difficult to ask the factory to reschedule, as their peak season is just starting. The production line's schedule is fully reserved and will be difficult, if not impossible, to change at this stage.
I await your urgent reply.
Our customer has only asked us to advance the schedules for July and August. Please keep the September schedule as is.
Hope this helps and properly interprets your meaning.