Won't send texts longer than 160 characters

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http://forums.androidcentral.com – So out of the blue my s3 decided that it will not send ANY texts longer than 160 characters. I've rebooted the phone several times, cleared data for the messaging app, deleted text history, none of that has worked. Before now, I could send texts of any length with no issue. Is there anything I can do? I have the stock OS (not rooted) and am using the stock messaging app. Is this a phone issue or a carrier issue? (HowTos)