Any 3rd party messaging apps that lack settings to adjust whether SMS is converted to MMS, or sent as multiple SMS, refuse to work on my S7, MM 6.0.1, US Cellular. So Hangouts, Facebook SMS & Signal Private Messenger for example, all lack settings to adjust how you want your messages sent. Any time I send a text using any app like this, if the length of the message exceeds like 160 characters (or whatever the limit is), I get a failed message error and the message fails to send. I have to stop typing and send, and then finish my message if I want to be able to use them. Some additional apps also display the same issue, even if the settings are there and I tell them to split the messages, but others don't. However, sending as MMS on third party apps work fine, as long as they convert anything over one text. Does anyone have any ideas on what would cause this?