Then [Barnabas] went to Tarsus to look for Saul, and when he had found him he brought him to Antioch. For a whole year they met with the church and taught a large number of people, and it was in Antioch that the disciples were first called Christians.
All that says is that it was in Antioch that the followers of Jesus were first called “Christians.” The Book of Acts contains all sorts of things that the Apostles and early Christian communities were doing before they ever received the official name of Christian. What does your friend think happened in the 9 years between Pentecost and Acts 11? Prior to Acts 11 there were conversions and baptisms due to the preaching of the Apostles. What does your friend think that they were converted to or baptized into if there was no church? There were so many converts that the Apostles had to appoint Deacons to take care of charitable works amongst the communities.