Cannot change DNS servers

[theskibug]

I already have my website built and working on a different host (cirtexhosting). But I needed to change the domain so bought theskibug.fr.
I need to change the DNS servers to point to my cirtexhosting and then they will change site to new domain.
The DNS servers are ns89.cirtexhosting.com ( 69.72.157.70) and ns90.cirtexhosting.com (69.72.157.71).
However, every time I try and change to these I get an 'action error' and cannot change the DNS servers.
This is now very frustrating and very urgent.
I opened a support ticket yesterday but have had no response.