If you can't verify online, one advantage to speaking directly with someone at the insurance company is you'll be more likely to get correct info, and exclusions and downgrades can be entered into your software. Also make sure you provide correct information and attachments otherwise you are bound to have trouble. This is a common problem.
If the patient is not sure of their insurance company or the phone number they will need to get the information and call back with it or, at the very least, bring it to the office at the first appointment. If the patient does not know their insurance information and can provide no information, they will be fully responsible for the total charges incurred and should be told this prior to being seated.