N-acetyl-alpha-D-galactosaminyl-(1->3)-N,N'-diacetyl-alpha-D-bacillosaminyl-tri-trans,hepta-cis-undecaprenyl diphosphate + UDP-N-acetyl-alpha-D-galactosamine = N-acetyl-alpha-D-galactosaminyl-(1->4)-N-acetyl-alpha-D-galactosaminyl-(1->3)-N,N'-diacetyl-alpha-D-bacillosaminyl-tri-trans,heptacis-undecaprenyl diphosphate + UDP + H(+) — reaction