Plan decrease invoice error

I have submitted several cases for our plan decrease, but it always came to same renewal manager, who can't update the case in reasonable period.  The longest waiting for update was 19 days...

Now the plan decrease finally settled, but the invoice was still wrong.  The old plan used a subtotal without original discount in last 5 years, so the proration credit was wrong.

Also it didn't have any backdate for downgraded plan, even when the delay was caused by the renewal manager's lack of update.  It wasn't "Zoom service effective date" listed on quotation either, which was already 1 month later than our original renewal date.

Now the new submitted billing error case was still assigned to this renewal manager.  I don't know if he recognized that his lack of update costed us over US$1000 on the inovice.  But we won't pay for his fault.

If he can't handle the case properly, someone in the community should be...