[VoiceOps] Grandstream call forwarding and local calling features

We primarily use their phones in a hosted service. A recent firmware change has made it so that call forwarding on the phone ONLY works if you have "enable local calling features" turned on. We always had it off, because we use *number for a lot of other special purposes. For example, *extension is to transfer calls directly to VM. *CO is each customer's conference bridge. Etc. If you enable local features, the phone traps anything that pattern matches their built in, partially undocumented codes. So a customer with extensions like 30x cannot dial *309 to send the call to VM. Anyone have ideas on this?