It is definitely not the phone, but Asterisk, because it works with 3CX as well with the same phone. You have already responded to a similar issue here, and this is exactly the same problem!
What I need is to park Callee Num +1 23 456 789!
[parking]
exten => 799,1,Answer()
same => n,Set(CALLER_ID=${CALLERID(num)}) <— SET THE CALLEE NUMBER +1 23 456 789
same => n,Park(LocationA-parking,CALLER_ID,300)[unpark]
exten => 800,1,Answer()
same => n,Transfer(sip:+1 23 456 789@parked)[parked]
exten => _X.,1,Answer() ← FETCH PARKED CALLEE NUMBER
…
I am pretty sure that 3CX uses the same approach for this. I need to be able to create a virtual SIP URI!