I just got a free text message from AT&T saying "Your new device requires a new SIM card to give you access to all services. Please visit your local ATT store to get a new SIM. Thanks." I am currently using the old SIM card from my iPhone 5 on my 6+ and it has been working without any issue. Do I really have to get an new SIM card? I'd like to avoid going to a AT&T store if possible Anyone else receive this? Thanks.