Which TV box do you have? If you're not sure, check here
Do you get any error messages/codes when you try to watch a film? That will help ID what the issue might be. Also whether you have the same issues with other OnDemand programmes - Sky OnDemand uses the same VOD platform as every other broadcaster (streaming apps excepted) so if you've got problems with one, you'll likely have problems with all.
It's hard to advise any further without knowing which model it is, but there's a few possibilities in each case...
A box swap will only be offered, if your box is deemed faulty - it certainly won't just be offered just because you have a particular model.
Let's check which model you have, then go from there.
I'm a Very Insightful Person, I'm here to share knowledge, I don't work for Virgin Media. Learn more
Have I helped? Click Mark as Helpful Answer or use Kudos to say thanks