Unless there is a lot more to the story, it is a scam. Here's a link that explains the IRS private collections process.
https://www.jacksonhewitt.com/tax-help/tax-tips-topics/back-taxes/what-happens-if-the-irs-sends-you-to-collections/
Calling the IRS directly should resolve the matter.
Also, a private contractor working legitimately for the IRS will not ask for payment to be made to the collections agency. The taxpayer will be told to make payments directly to the IRS.
https://www.consumerreports.org/consumerist/the-irs-is-now-using-private-debt-collectors-heres-what-you-need-to-know/
From the link:
In fact, taxpayers won’t even be asked to pay the private debt collectors.
Instead, these collectors will provide information about electronic payment options for taxpayers on IRS.gov/Pay.
Any payment by check should be payable to the U.S. Treasury and sent directly to IRS, not to the private collection agency, the IRS notes.