It would come down to your word against the vendors in the resolution center. You can't 'prove' anything beyond stating your case and proposing a resolution. If the vendor rejects the proposal it will come down to an admin reviewing the case, if your situation is a one off you probably will not get very far, if there are others making similar complaints you may be in with a stronger chance. It is impossible to predict the outcome of a resolution matter as every case is different.