Pre-Paid Post item lost. Issue with contacting company and claim.

Ryan2903

Hi, I am looking for advice regarding a tech company who recycle old phones. MCRecycle. I sold my old phone to this company and used the pre-paid postal method. The item was sent on 11th April 2020 and after a month with no contact, I checked the tracking number, contacted Royal Mail and the item is infact missing. 
I have sent emails to the company explaining the situation and also tried to phone them but I have receive no reply or call back.
The problem is that I cannot make a claim for the item via Royal Mail because the sender is MCRecycle due to the post being pre-paid! As I cannot contact the company and Royal Mail claims only consider claims made within 80days, I am stuck and do not know what to do. and the clock is ticking! 

My phone was sold for £140 however I will only receive payment once MCRecycle have tested the phone. Obviously they will not be able to do that now, all that is required is for MCRecyle to request £140 from Royal Mail to cover the value however I cannot get in contact with them.
Can anyone recommend what I should do next?

Thank you

Ryan