Perform a String Query

Personal I have the following method and Query:

mt_dispositivo = MtDispositivo
    .where("id_conta = 28 or id_conta = 29 or id_conta = 30 or id_conta = 36")
    .select('nome, data_criacao, data_atualizacao, tipo_conexao, is_online, status_atualizacao, geolocalizacao_endereco')   

    send_data mt_dispositivo.to_xls(:except => [:id_conta], content_type: 'application/vnd.ms-excel', filename: 'mt_dispositivo.xls')

This method makes Excel Download as an ID and other attributes of all  Customers that are Online. I need to do a String query that returns only those that contain in  start: "BS, FS, SR and FNAC"

How would you look?