IP Phone acquire untagged VLAN IP instead of tagged VLAN

[f.pancani]

Good morning, i have an issue with all the IP Phone in my company, i mainly have Yealink T23P phone but the issue appear even on other models.

I have a switch L2 infrastructure made by Huawei S5700 Switch POE where my IP Phone are connected.
For example purposes we have VLAN 1 and VLAN 2
All the port in my switch are set like this:
TAG VLAN 2
UNTAG VLAN 1
The IP Phone are configured like (Firmware 44.82.0.20):
WAN Port: VLAN ENABLED on VLAN 2
PC Port: VLAN DISABLED
LLDP: Disabled
There are NO other setting configured.

What happen is that, if i connect the IP Phone to one of those ports, it acquire an IP from the VLAN 1 instead of VLAN 2, even though i had told the phone to use the TAG on WAN Port.

That's what happen with a HUAWEI S5700 Switch.
In order to exclude a switch problem i took a new switch and a new device, set the LAN port TAGGED on VLAN 2, the above-mentioned device join the correct VLAN with the correct IP Address.
Today i came back to the office and i recreated the environment on a Cisco 3750 Switch, the IP Phone TAG itself on the correct VLAN and everything seem to work.

So the issue seems to be related to the couple Yealink/Huawei.
Any advice?