who do I contact to verify my invention?

The terms 'verify' and 'certify' are not used when dealing with inventions, so I'm not sure what you mean. But if you want to get a patent you have a long road ahead of you. The first thing is to search the patent archives to see if there is an existing patent for you idea. Then you must file an application for patent and send it to the US Patent and Trademark Office in Washington DC (www.uspto.gov) who will eventually review it and send you a response. This response must then be acted on by you depending on what they have to say. After that they may decide to issue you a patent.

These actions are not required for you to sell a product. It does offer you court protection if someone decides to steal your idea. But only if a patent is granted. A good patent lawyer would be very helpful in this. That's lawyer, not service. Patent service firms are a rip off.