IPhone :: Why Do Some Texts Not Identify The Sender Although They Are In Contacts

Not sure if this issue is related, but I changed my apple ID password yesterday, and this morning, my Iphone asked for my password before I could read an incoming text from a contact that is already stored in my iphone. And since then, text messages from some of my contacts, when I look in the "messages" identify the incoming message's sender not by their appropriate contact name I have stored in my iphone for them, but instead identifies them as " +1 and the phone number of that contact." For example if I have a friend stored as Susan in my contacts, but for some reason when I send a text or receive one from that contact, it doesn't identfy the sender as Susan but lists her number with a " +1 " before it (the number isn't stored with a +1 in my contacts).