Shockingly bad service.

Shockingly bad service.
Sent over a Samsung phone to sell on the 27th of July using their freepost label. Included all of the references and order number. At first they claimed to not have received it but upon looking at the tracking it clearly shows that they have picked up. Since then I've only had one contact with them despite phoning up several times a day. I still don't know if they will honour the price they quoted or even if they still have it! It's now been an entire month. When can I expect to know where I stand with this?