Hello @crs5 ,
Absolutely! If you purchase any piece of equipment or anything else that you use exclusively in your business, you can claim it as a 100% business expense.
In the case of a cell phone, you will want to add the cost of the phone in your taxes as an asset under the Self Employment section of TurboTax (it is at the bottom of the page). If the item costed under $2,500 you will be able to elect to expense the entire cost of the phone in the current tax year. TurboTax will ask you all those relevant questions.
For the service, you will want to add the total cost of the service for the entire year under the "Communication" category of your expenses.