A disagreement over the correct customer service line aboard a Carnival Cruise Line ship has now escalated into a federal case. According to Fox10 , two women who got into a physical altercation aboard the Carnival Spirit earlier this year are facing federal simple assault citations after investigators reviewed surveillance footage and interviewed witnesses following the incident. According to court filings, the confrontation happened in March as the ship was returning to Mobile, Alabama, from the Bahamas, but the two women appeared in federal court this week to answer the charges. Federal records state the argument began inside an onboard service area where passengers were waiting to settle charges on their cruise accounts. Investigators said Tonya Nelson approached Lisa Horace and her husband to tell them they were standing in the wrong line, reportedly pointing to signage indicating the area was reserved for diamond and platinum loyalty members. What started as a disagreement quickly turned physical.…