The two options that have been included in grandstream firmware version 18.104.22.168 under Settings -> Programmable Keys -> Virtual Multi-Purpose Keys Setting, Transfer Mode via VPK Enable transfer via non-Transfer MPK has been in my opinion very very very inconvenient. I'm not sure what was the expected behaviour by grandstream but transfers doesn't work correctly after those two features had been added unless you configure them as follows, Transfer Mode via VPK = New Call Enable transfer via non-Transfer MPK = No Those values combined with Attended Transfer Mode = Dynamic under Settings -> Call Features, which enables attended and blind transfers, restores what's for me the expected transfer behaviour. And the only benefit I had seen from using other values for those two new options (Transfer Mode via VPK and Enable transfer via non-Transfer MPK) is that you can make attended or blind transfers (depending on configuration of those options) just by clicking one BLF key or VPK key. But making a transfer just by pressing one key (BLF) instead of two keys (transfer key + BLF) doesn't worth losing so many other features people are used to. To name a few I have detected (and some unhappy customers): Capture speed dial key only works with phone on hook. Probably same for any speed dial which will only work on hook (if Enable transfer via non-Transfer MPK is set to yes). BLF capture only works on hook (if Enable transfer via non-Transfer MPK is set to yes). Once you send attended transfer via BLF, you can't just hangup the phone before your partner pickups the call to make blind transfer. You can't press dial key to start an attended transfer after pressing transfer button + dial extension number. Nor hangup to make it a blind transfer. And probably some more strange behaviours. For me doesn't worth to break so many features that users of the phones are used to just in exchange of one enhancement. Besides it is a lot of time lost to explain new behaviour to customers.