Andy Wade wrote:

Yes, to a DC voltage a Capacitor has infinite resistance because it is
open circuit!

But if the 'DC' voltage changes a current will flow,

If it changes, then it isn't DC (for the purposes of reactive theory),
you've imposed some AC component upon it. It may be of very low
frequency, but it's still an AC component and thus the impedance of the
capacitor is no longer infinite.