[UT] Garnishment on fake dentist debt help!

My boyfriend recently received notice he would get garnished for an unpaid dentist visit bill that went to collections. The problem is the visit was back nesrly 10 years ago and he doesn't recall the visit and both dentist and office don't look familiar at all. The collector he's spoke with will only provide a breakdown of total collections fees and list of dentist fees for services done, but otherwise no info to prove it was him. Dentist bill was only a couple hundred but collector now wants close to $1k in fees. He's tried calling the dentist directly and was not able to get any help. Googling the debt collector pulls up multiple links to suggest scams and predatory collecting.

What options does he have? Aren't debt collectors responsible for providing proof to validate the debt? He's never received any prior notice of debt either, this is news to him. Isn't the statute of limitations on debt collection something like 6 years in UT?