tax rate mimatch

we wrongly charged gst @ 18% in the month of July instead of @ 28%
and in the month of Aug we have raised Dr note to customer for gst tax difference rate 28 -18 =10%
now we have filing gstr 1 for the month of Aug we have face problem related to tax rate because tax rate of gst as per govt is 3,5,12,18 & 28%, now how can we process our return .please suggest me