The Mitel's embedded VM doesn't have a "General Delivery Mailbox", when a call is transferred via a single digit mailbox, it says "Your call is being transferred to <ext # if no name is recorded, or name recorded on destination mailbox>". The only mailbox with a pre-recorded name is the operator mailbox 0, and it is literally recorded as "the operator"
Look in form 50 and find mailbox 2 and see the destination (extension) of that transfer only mailbox and log into it and check the recording for the Name in that mailbox.