My W2 marked statutory employee. Can I write off my cell phone and car insurance?

Yes.  If you are a statutory employee, you are able to take business deductions. 

However, you can only deduct the portion of your cell phone bill that is work related.

Your vehicle expenses are only deductible IF you are driving to more than one location.  If you have only one or two clients that you regularly visit, this would be considered commuting or like driving to the office and that is not deductible.  

If you visit multiple people and do not have a fixed location, you would be able to deduct your mileage or actual vehicle expenses traveling to all the different houses. You would need to have tracked your miles so you know how much is business and how much is personal.

Taking Business Tax Deductions