It's no problem! From the help file....good idea not to have a space at the end though.....
Name:
This is the user's account name, eg. "JohnB" and the one that will be used for RAS Dial In, Caller Display and voicemail mailbox. As the display on Caller Display telephones is normally only 16 digits long it is useful to keep the name short. Only alphanumeric characters and space are supported in this field. Do not use punctuation characters such as #, ?, /, -, _ and ,. This field is case sensitive and must be unique.