As of 12/14 at 8:30, AT&T calling test indicate that the update made yesterday has addressed the AT&T calling issue, related the transferring calls.
Sometime around 12/5/22, AT&T released codec variations for their inbound callers that created the issue. BISD had a set codec that was in use, g711, for call quality reasoning. Call "codecs" control the different call quality levels. When a call transfer was attempted (either by an auto attendant or User), the call setup process to the Microsoft cloud service was being rejected due to the mismatch in codecs within the message header, thus Microsoft was rejected the call transfer.
As this issue was created by the provider AT&T, the work around was to update the SBC IP profile "IPP_Teams" (session border controller) to allow all inbound calling codecs, thus passing on the variations of calling codecs to Microsoft for transfer purposes.