It's not C. armandii, not sure what it is without knowing what the flowers were like. You can trim it back a bit, but early flowering clematis don't generally get pruned much, other than a tidy up.

Ok thanks Bamboo

It's probably an alpina or macropetala, but impossible to say which one without having seen the flowers. Neither species needs any pruning, except to tidy it up or keep it within bounds if necessary.