configure freeradius to use UPN instead of samaccountname

We have our freeradius setup to authenticate with Active Directory for EAP. Currently, it uses the samaccountname but we want to use UPN instead. We get "NT_STATUS_NO_SUCH_USER" when testing with ntlm through command line. ntlm_auth --request-nt-key --domain=test.local --username=tuser@pub.com Can you please let us know what needs to be configured to support the UPN? Thanks.