Traveled to Mexico, phone and texts worked fine. After returning to CA, I have 2 recipients, if I text them, the reply is returned with the Mexico country code 044 added ahead of their number, and a new text thread is started (and their contact info is now unknown).
For example text to # 408-555-1212, reply comes from 044-408-555-1212 unknown contact. This happens with group texts also, with a new group thread started, but only happens to the same 2 recipients - who happen to have iPhones. I have MOT Z Droid.
If I reply to the 044... message, all is lost (in group texts, all receive text, except the 044 recipient.
Issue appears to be fixed by removing "1" before the phone number of the 2 recipients in contacts. [044 usage in Mexico was/is a prefix used when dialing from a landline to a cell phone, to bill the landline for the call. Wierd stuff happens.] Thank you for the fix.