The Texas Department of Public Safety's Capitol Police have started a criminal investigation of fraudulent use of the state's long-distance phone network by college students who apparently got hold of agency calling card numbers. So far, that investigation involves four state agencies whose phone usage recently took unexpectedly large jumps. The investigators think college students across Texas have been using calling card codes to steal tens of thousands of dollars worth of phone time from the state's Tex-an (pronounced Techs-ANN) phone system.