Can I get a Turbo Tax Service Code since I am using Turbo Tax for my clients?

You cannot use TurboTax if you are being paid to prepare tax returns for "clients."  That is a violation of the terms of service.   TurboTax is software for a self-prepared return--for use by individuals and their family members.  

You can not use the Online versions or the personal Desktop Software to prepare returns for clients. Intuit has 2 products for tax preparers. They are Lacerte and ProSeries. ProSeries is the least expensive. You can install ProSeries and Turbo Tax on the same computer.

Intuit Products for Tax Professionals,
https://taxpro.intuit.com