W52P not working after change of broadband supplier

[Jasibansel]

Hi,
Complete idiot with technology so please be gentle.
We are a small UK business with a W52P handset which we used for many years with a BT cloud phone system. We changed supplier to Vodafone, got a full fibre line and a superhub but now we cannot make the yealink phone work at all, it just says "No matched line". Vodafone confirm we have an active line, (new number not the old cloud number). They suggested the phone may be tethered to BT and to ask for the RPS to be removed. We have requested that by ticket to Yealink but they say the MAC address isn't on their system. What do we do next? Do we just have to buy a new phone handset? Thansk you to anyone with any wisdom.