SIP-T22P with CISCO CALLMANAGER 8.6 with LDAP integration

[lecuonai]

I would like to register SIP-T22P Yealink phones on a Callmanager 8.6 with LDAP integration.

The main problem is creating an account for Yealink phone SIP-T22P on Callmanager.
If I use an account with username of only letters, for example MARTINEZAE, and enter it at the phone's configuration, it doesn't take the registered state, and is Rejected from the Callmanager.
But if the account is only numbers, for example 22301 - it successfully registrates and works.
I updated the firmware with the last version, but the problem still exists.

I will appreciate your help because i have a deadline to put on work this architecture with a username of only letters
( 400 phones to be used with the Cisco Callmanager )

Thanks in advance
Isabel