Who did the prostitute girlfriend call?

I believe she called the new girlfriend (one who majored in French literature). This would explain his cold reception when he went to her apartment asking to stay for a few days.

"He killed sixteen Czechoslovakians. Guy was an interior decorator."

Yes, Victoria called René's number and either explained the situation to him and/or his wife. Rene probably told Victoria that Simon was hustling him for more money and threaten to go to the cops.