Catalysis of the reaction: N-acetylneuraminyl-2,3-alpha-D-galactosyl-1,4-beta-D-glucosylceramide + UDP-N-acetylgalactosamine = N-acetyl-beta-D-galactosaminyl-1,4-(N-acetyl-alpha-neuraminyl-2,3)-beta-D-galactosyl-1,4-beta-D-glucosylceramide + UDP.
uridine diphosphoacetylgalactosamine-acetylneuraminyl(alpha2->3)galactosyl(beta1->4)glucosyl beta1->4-acetylgalactosaminyltransferase activity