You can do that if you don’t wish to contract with them. A friend of mine used their cellphone light to shine through a letter received and they were able to read the letter and discern that they did not want to contract and they sent it back with what you are talking about written on the envelope. If you decide to do that make sure you photograph the envelope before sending it back. They sometimes send them out again up to three times but if that happens just repeat the action (if that is the course of action you take)