HELP!! Lost contact Info on iPhone since latest update

How do I fix my phone? My phone was working perfectly until the latest update. The errors started immediately after the update was installed. I receive text messages from contacts existing in my contact list and then their information disappears and only a number shows up. I go into my contact list to send a text to an existing contact. They respond and their contact info is then deleted and only a number appears.. I have lost names, phone numbers, addresses, birthdates, and important notes under the contacts. This is extremely frustrating!!! My iphone is less than a year old.. please help!!!!