Catalysis of the reaction: phosphate + beta-D-galactopyranosyl-(1->3)-N-acetyl-D-glucosamine = N-acetyl-D-glucosamine + alpha-D-galactopyranose 1-phosphate.
beta-D-galactopyranosyl-(1,3)-N-acetyl-D-hexosamine:phosphate galactosyltransferase activity