Likely a ligustrum that may have copper or nutrient deficiency so the leaves aren't their normal dark green.
If the leaves are longer than 3 inches, it lis likely wax leaf ligustrum. If closer to 2 inches it may be L. obtusifolium or border ligustrum.
A few key characteristics of ligustrum (in addition to the opposite leaves) include raised veins on the underside of the leaf and small white spots (lenticles) on the limbs and branches.
The ligustrums as a genus are all invasive. If you have a creek nearby they will likely escape there and could dominate its understory in 20 years. I wouldn't plant a tree I thought was a ligustrum on my property, but you can do what you want.
If you decide to take it back you can tell them it isn't a laurel (not alternate leaves). Native alternatives that look somewhat similar in size / form are rusty blackhaw viburnum or ilex decidua.
