SQL Querry optimization and improvements

Our primary service is to rent mobile phone lines and we need to audit the phone bills that we get to see that the mobile operator is charging us correctly and also need to bill the end users. We have stored procedures that create both the audit and the re-bill reports on excel but we need to add a few feilds to the reports and make some other improvements like try to shorten the time that the current sp takes to finish and generate a report. Our objective is to start with VERY simple task so that the developer can gradually become familiar with the DB to then continuously make new reports, improvements etc. Our current SQL sepcialist is no longer able to do freelance for lack of time. Please bid for this simple task only if your looking to do ongoing work because it will take some time to become familiar with the entire DB structure.