Nameserver Error Message

I am attempting to transfer the domain www.crowesbar.com as the owner wants somebody else to take it over .
The new company taking control have asked me to change the nameservers setting to

ns1.rmedia.ie

ns2.rmedia.ie

When I try to do this I am getting this message

One or more of the nameservers you entered cannot be verified as an accurate nameserver. Please double check your entry, and if you have any questions contact the registrar to which you are attempting to direct your domain.

Can you please advise.
Thankyou