Eventually, being able to move or have both hands free to work and talk or listen is a part of most users' experience, especially if they are on the phone a lot. So we get this question from time to time, lets break down some of the options out there.
For desk phones, your best bet is to check the options available by the headset manufacturers. Traditionally, the major headset manufactures have been Jabra and Poly, formerly Plantronics. Both of these companies have compatibility tools online that help you sort their product by the make and model of your desk phones. The most significant advantage to these is these tools also tell you if you need specific settings on the headset or additional adapters for features like EHS to answer ringing calls from the headset. Once you have narrowed down your options, I would encourage taking that part number on a little internet shopping trip to see who has the best prices. Most of these will be available from Amazon and other online retailers.
https://www.jabra.com/compatibilityguide/
https://www.poly.com/us/en/product-finder
There are some newcomers in the headset marketplace, for example, Yealink has introduced a line of wired and wireless headsets, including USB-based headsets you can also use with your computer for softphones.
https://www.yealink.com/products_list_44.html#filter2
Speaking of softphones, because these are PC/Mac applications, any USB headset is typically compatible. In fact, many of our own staff use Logitech gaming headsets for the comfort and ease of use with softphones and their laptops.
Some of the things to keep in mind, when it comes to phone calls and audio quality, the weakest link in the connection from agent to caller will make all the difference in the quality of the call. The best internet connection, local network, desk phone, etc can all be unrivaled by a low-quality headset. The same goes for softphones, maybe even more so because USB headset options are so prolific. The same can be said of Bluetooth headsets on softphones, mobile app, and support desk phones. The quality of the headset will make or break that caller experience. So before going all-in on some new brand or model, test, read reviews, kick the tires and take your time finding a good headset. It is not always the most expensive headset, but it is always worth taking your time.