DHCP issue on Yealink phones with HP Switch HP2920

[Crizz]

Hello everyone,
We’ve got a new HP Switch HP2920 – 24 - layer 3.
We have configured the following simple 2 VLAN’s:
= = = = = = = = = = = = = = = = = = = = = = = = =
hostname "HP-2920-24G"
module 1 type j9726a
snmp-server community "public" unrestricted
oobm
ip address dhcp-bootp
exit
vlan 1
name "DEFAULT_VLAN"
no untagged 4,10-20
untagged 1-3,5-9,21-24,A1-A2,B1-B2
ip address 20.1.10.33 255.255.255.0
exit
vlan 50
name "VLAN50"
untagged 4,10-20
ip address 20.1.50.10 255.255.255.0
ip helper-address 20.1.10.240
exit
no dhcp config-file-update
no dhcp image-file-update
password manager
= = = = = = = = = = = = = = = = = = = = = = = = = = = =
OUR LAB NETWORK:
VLAN1 – 20.1.10.X - default DATA
VLAN 50 – 20.1.50.X used for the IP Telephony.
DHCP server - 20.1.10.240 [Windows server 2008 R2]
Yealink phones T22 and T42G.
Switch port 1 – is going to FW interface for default VLAN 1.
Switch port 4 – is going to FW interface for VLAN 50.
Before I will test the provisioning with 3CX PBX we have the next issue:
PROBLEM:
Even though I have set up “ip helper-address 20.1.10.240” for Vlan 50, Yealink phones are NOT getting IP addresses on VLAN 50, but are getting IP’s on default VLAN 1.
The computers are getting DHCP IP addresses on Vlan 1 or Vlan 50. No issue with the computers.
I have tried to add voice command on the VLAN 50 and didn’t work.
I have tried to disable the LLDP on Yealink phone but didn’t help.
Can anyone faced the same issue before?
Thank you very much in advance.
Crizz.