Be aware that the web-based system Medicare provides to help you find a doctor is quite poor. The database which contains provider information is notoriously full of incorrect information. Pulmonologists are listed as gynecologists. Dentists are listed as psychiatrists. You also may wind up with a list of providers meeting your search criteria (the software allows very few search criteria), and when you call any of the numbers given for them, you will be told that provider has never worked there and they know nothing of him.
The web interface is also quite badly designed, and makes it very hard to get down to the contact data you need. It is slow, and is also designed such that, if you need to restart your browser, all your search data will be lost and you will have to begin all over again. Contact information is not displayed until you drill down to it with many clicks. If you take too long, your session will time out and your data will be lost. You cannot force the system to simply give you all the information at once, so you can save it and examine it later. There is no way to print out all the information from a list of hits so you can take time and research providers at your own pace. There is a feature to print out data to PDF, but, surprise!, it's just a list of names! The site withholds all contact information from such a print out.
The telephone service is even worse.
It's not clear if Medicare deliberately has chosen to make it nearly impossible to find a provider, so as to minimize the services delivered to Medicare beneficiaries and thus program outlays, or if Medicare's badly designed systems are just another example of inept government, but in any case, prepare yourself for a long, arduous search if you attempt to find any kind of provider using the methods provided by Medicare.