I have a new iphone 5S, and I receive an error message when texting two of my family members? The message is "+1 (216) 116-, 566-4699Error invalid number. Please resend using a valid 10 digit mobile number. I am using the correct area code (616) when typing in the 566 4699 number. All other texting is sent without a problem?? The sales people at the ATT store could not help me, and told me to contact ATT! I usually get more results using this forum. Any help out there??