Premium hosting doesn’t make you immune to DDoS attacks. It can endure bigger attacks before having problems (because there’s more server power and network capacity) but if you move your site to iFastNet and it still gets a DDoS attack that’s large enough to cause problems, they’ll still suspend you.
The free hosting servers do have DDoS protection. But that doesn’t make them immune to a large and/or direct attack.
While you can’t make DDoS attacks impossible, you can add protection if you have a custom domian by using Cloudflare.
But again, this does not make you immune- nothing does. But it does add another layer of protection when used properly, so it’s still worth setting up.