Change Nameservers

Hi i setup my website on the free service and realised  it was going to be not very good for SSH as it had to be renewed every 3 months and would not give me a green padlock…Any way i upgraded to a paid account through the link on infinity free to a paid account to ifastnet.com. When i tried to move my site i was asked for an AUTH code but could not find it on infinity free so i was told to change Nameservers to ns1.ifastnet16.org and ns2.ifastnet16.org however nothing has changed…
How do i get things right

Nameserver records returned by the parent servers are:

ns1.epizy.com.   [‘198.251.86.152’]   [TTL=172800] 
ns2.epizy.com.   [‘198.251.86.153’]   [TTL=172800] 

I need to change to

ns1.ifastnet.16.org
ns2.ifastnet.16.org

Please help

The AUTH CODE is typically used to transfer a domain name. This code can be provided by the current registrar of the domain. Alternatively, you could change your domain's nameservers, but that's also something that has to be done through the domain registrar.

The domain registrar is the company through whom you've purchased your domain name. We're not a domain registrar, we're only a hosting provider, so I can't give you your transfer auth code or change your nameservers from my end.

The only exception are the free subdomains we provide. However, free subdomains cannot be pointed to other nameservers or be transferred to other companies. You can migrate our free subdomains to iFastNet, but you'll have to ask iFastNet to pull the subdomains in.