That post was made months ago, it would be better to contact him through TradeManager. But I think I can help you with this one.
It's typical for UK scammers to have non-working landline numbers, and a working forwarding number. I tried that number and it doesn't work. The number starting with +4470 is a type of premium number that is free to set up and receive calls to, and that can be forwarded to anywhere in the world. Few legitimate companies use them.
If you check them out with the Companies House, you will see their Nature of Business listed as "Manufacture computers & process equipment". That has very little to do with selling mobile phones. It's also typical for these scammers to copy a registered company like this and impersonate them.
Their English is also very bad for a UK company.
I already answered this here:
This seems to actually be a real company rather than a typical scam. If you believe you have been scammed, I would recommend you try to deal with it through legal channels. Though depending on how much you lost it may not be worth it.