What are the specific phone models?

Thanks John , that just about what the people at wal mart were attempting to tell us whilst also trying to get us to purchase about $400 worth of new phones for the 4 that wont work .. I hate to ask but could you tell me how to reset the connection to another tower . I really don't know how . I can disable them , take the batteries out and all but not reset a tower connection . Thank you .

Something is wrong with the tower that they are connected to. I would power off all of the phone and let them reconnect to another tower and reset the connection to the existing tower. Take out the battery for a couple min if possible.

I really do not know what to do either..This family has 4 cells. 2 smart phones. one beginner phone for my texting photo taking tween and my husbands plain one that does do internet / text/ camera etc but that's about all it does. 2 are from straight talk , 2 are from the sprint (I wireless network) . We've had these phones for months now and the numbers for years . Suddenly at 7 am Friday they all stopped at once incoming or outgoing anything. All phones that take wifi are getting good signal. We have all bars on all of them . you call and you hear silence , then a few busy signals the silence again - disconnect . We leave ONE mile from the Apt and they all work fine again . I cannot imagine what has happened, but something has. Does anyone have any ideas on how to get them to work In the house again . Again , this happened suddenly , all at once. One of them is my business phone so that is a nitemare unto itself .