Elvox 620R loud noise from picking up handset

[lag93]

Hey, we recently just had a new handset installed in our flat (801>620) but about a day after installation the handset makes this noise when it's picked up. https://youtube.com/shorts/lc-DXLDP1do?feature=share the noise can be heard on the outside aswell without buzzing the flat first. Thanks for any help

 

[sparkymarka]

Get them back to sort it ….