I receive a cell phone allowance/reimbursement from my employer which pays for a work-only cell phone. How do I report excess allowance?

This is a phone that I ONLY use for work.  The arrangement changed from a cell phone "allowance" to a cell phone "reimbursement" halfway through the year.  The amount was reported on my W-2 but in box 14 (other) as CELLPHONE.  However, my allowance exceeded the amount I spent.