Cell phone business deduction

I  understand how to assign business vs personal use for my cell phone bill

 

My cell phone itself was purchased 2021...but the payments are spread over the length of my contract. Do i still use the whole cost of the phone (subject to business percent use) on this years taxes or only as the payments are made

I would think the whole cost as a business asset goes on this year as if I paid for the whole thing this year