Report "I have an extra handset for this E5640 model and it asks for the Base Unit ID number which is 15 digits (actually 13 with two spaces). Normally you can use the # or arrow key to move the cursor and create a space when entering a name in the directory; however those keys do not work until the Base ID number is actually completed and registered as correct. How do I move the cursor and complete the whole 15 digit string it wants? Other AT&T phones use this same method so even if you don't have this particular model, your method should work for mine. I've also tried using a 0 and the * but they don't work either. ATT won't help because the phone is out of warranty. Can you help?"