Whatsapp messages disappearing

I find that many of my recent Whatsapp messages have disappeared from my smartphone.I did not delete them.I am discovering many other people have similar problems.

                            I had my latest updated version of Whatsapp downloaded at the Rogers service centre by a very helpful employee.Unfortunately he was not there later when I discovered several of my recent messages on Whatsapp had disappeared.

                             I contacted Chatr customer service representatives and others but they were  all either unwilling or unable to help.Apparently my new version of Whatsapp has a setting that erases new messages within 7 days.I want to undo that setting and restore lost messages.I go running around in circles.

                      Hope somebody will help me.We should all be able to restore old,lost Whatsapp messages-especially if we did not delete them.