My parents are on our family plan, and they receive texts fine but have been unable to send them. This has only just begun happening in the last month. They've tried sending texts using wifi on and off with the same results. Twice they restarted their phone and all the previous texts they tried sending then went out. Of course they don't want to continuously have to restart the phone. Any ideas of whether it could be something in their settings or is it more likely to be a problem with their phone?