Bad after sale service!

I ordered a substantial amount of A2 posters which are more expensive than A3 posters and I received A3 posters instead. Printulu has said they weighed the parcel before dispatch and it was a similar weight to that of A2 posters. I am no fool I have ordered from them many times, a simple Google search also shows us that A2 posters and A3 are very different in size!!!